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7 May 2013

Volume 113, Issue 17, Articles (17xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 113, 174302 (2013); http://dx.doi.org/10.1063/1.4798262 (4 pages)

Yuichiro Kurokawa, Takehiko Hihara, and Ikuo Ichinose
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back to top Magnetoelectronic Effects

Electric-voltage control of magnetism in Fe/BaTiO3 heterostructured multiferroics

G. Venkataiah, E. Wada, H. Taniguchi, M. Itoh, and T. Taniyama

J. Appl. Phys. 113, 17C701 (2013); http://dx.doi.org/10.1063/1.4793511 (3 pages)

Online Publication Date: 25 February 2013

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Electric field (E) control of the magnetic anisotropy and coercivity (HC) of a Fe film in Fe/BaTiO3 (BTO) is demonstrated at room temperature in the tetragonal phase of BTO. Polarizing microscopy and x-ray diffraction analysis of BTO (001) surface show distinctly two different regions; one with a1, a2 and c domains separated by 180° and 90° domain boundaries (DBs) (region 1) and the other with a1 domains separated by 180° DBs (region 2). The Fe film on region 1 shows complex magnetic anisotropy with the net magnetic easy axis in between [100] and [110] directions of BTO, while the magnetic anisotropy in region 2 exhibits two fold symmetry with an easy axis along [100]. In applied electric field (±10 kV/cm), the magnetic easy axis of the Fe film in region 1 is switched to the [110] direction of BTO, whereas in region 2 it stays unaffected. The HC versus E curves in region 1 show a butterfly-like behavior, while in region 2 no changes are observed. Also, the HC measured in E = ±10 kV/cm at different magnetic field orientations shows dramatic changes in region 1 compared to region 2. The observed electric field dependent magnetic response in both regions can be understood based on the DBs modifications and associated strain effects.
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75.85.+t Magnetoelectric effects, multiferroics
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

First principles study of magnetic anisotropy and magnetoelectric effect of FePd/MgO(001) ultrathin films

K. H. He and J. S. Chen

J. Appl. Phys. 113, 17C702 (2013); http://dx.doi.org/10.1063/1.4793601 (3 pages)

Online Publication Date: 26 February 2013

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The magnetic anisotropy and magnetoelectric effect of FePd/MgO(001) ultrathin films were studied by first principles calculations. The calculation results showed that the magnetization easy axis was in the film normal and the magnetic anisotropy energy (MAE) was reduced with the film thickness. Furthermore, the MAE of FePd reached maximum at the lattice constant of 4.05 Å. The MAE of FePd/MgO films decreased with increasing applied electric field, and the magnitude of the interfacial magnetoelectric coefficient was about 1.4 × 10−12 G cm2/V, which was larger than that in previous reports of Fe/MgO. The calculations also suggested that the MAE was largely dependent on the difference in the orbital moment between [001] and [100] magnetization directions.
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75.30.Gw Magnetic anisotropy
75.60.Jk Magnetization reversal mechanisms
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.85.+t Magnetoelectric effects, multiferroics
77.55.Nv Multiferroic/magnetoelectric films

Room temperature magnetoelectric effects in bulk poly-crystalline materials of M- and Z-type hexaferrites

Khabat Ebnabbasi, Marjan Mohebbi, and Carmine Vittoria

J. Appl. Phys. 113, 17C703 (2013); http://dx.doi.org/10.1063/1.4793606 (3 pages) | Cited 2 times

Online Publication Date: 27 February 2013

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The converse magnetoelectric effect in poly-crystalline Z-type, Sr3Co2Fe24O41, and M-type, SrCo2Ti2Fe8O19 (SCTFO), hexaferrite materials are reported. The change in remanent magnetization (Mr) for M-SCTFO sintered in oxygen and sintered in air is similar and approximately equals to ∼3% in 13 kV/cm electric field and for Z-type is ∼12% in ∼10 kV/cm electric field. The measured magnetoelectric coupling coefficient, α, values at room temperature for Z-type and M-type hexaferrites sintered in O2 were measured to be 7.6 × 10−10  sm−1 and 2.4 × 10−10  sm−1, respectively. Sintering the M-type in air reduced to 1.7 × 10−10  sm−1. As it is well known, lack of oxygen in local oxygen sites implies lower resistivity and a modified magnetic structures or state. However, in magnetoelectric hexaferrites, there is an additional effect due to lack of oxygen, and the spin spiral configuration is significantly modified to lower the induced magnetization upon the application of a DC voltage or electric field.
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75.85.+t Magnetoelectric effects, multiferroics
75.50.Gg Ferrimagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
72.20.My Galvanomagnetic and other magnetotransport effects

Magnetic field tunable acoustic resonator with ferromagnetic-ferroelectric layered structure

Natalia Polzikova, Sergey Alekseev, Iosif Kotelyanskii, Alexander Raevskiy, and Yuri Fetisov

J. Appl. Phys. 113, 17C704 (2013); http://dx.doi.org/10.1063/1.4793774 (3 pages)

Online Publication Date: 28 February 2013

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High overtone acoustic resonator with yttrium iron garnet/zinc oxide layered structure was theoretically considered, fabricated, and experimentally investigated. The theory of the resonator, containing an arbitrary number of magnetic and nonmagnetic dielectric/ferroelectric layers, placed in a transverse magnetic field is presented. The simulation shows the possibility to tune the resonant frequency in the range of ±1 MHz by magnetic field. This tuning is due to the resonance magnetoelastic interaction in the saturated ferrite film and the total phase shift of acoustic wave in the structure. The experiment proves the magnetic field influence on resonance frequencies and attenuation of transverse wave with polarization vector quasicollinear with the field direction. The tuning about 0.25 MHz near the acoustic resonant frequency 2 GHz was obtained in the field 260 Oe. This frequency is close to the ferromagnetic resonance frequency in ferrite film, corresponding to the field applied.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.55.-g Dielectric thin films
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Gg Ferrimagnetics
75.80.+q Magnetomechanical effects, magnetostriction
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

In-plane anisotropic converse magnetoelectric coupling effect in FeGa/polyvinylidene fluoride heterostructure films

Zhenghu Zuo, Qingfeng Zhan, Guohong Dai, Bin Chen, Xiaoshan Zhang, Huali Yang, Yiwei Liu, and Run-Wei Li

J. Appl. Phys. 113, 17C705 (2013); http://dx.doi.org/10.1063/1.4793780 (3 pages)

Online Publication Date: 4 March 2013

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We investigated the converse magnetoelectric (CME) effect in the Fe81Ga19/polyvinylidene fluoride (PVDF) heterostructure films. A weak in-plane uniaxial magnetic anisotropy was observed in the as-deposited magnetostrictive FeGa films. When a positive (negative) electric field is applied on the ferroelectric PVDF substrates, both the coercivity and the squareness of magnetic hysteresis loops of FeGa films for the magnetic field parallel to the easy axis become larger (smaller), but for the magnetic field parallel to the hard axis the coercivity and the remanence get smaller (larger), indicating an anisotropic CME effect in FeGa/PVDF heterostructure films.
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77.55.Nv Multiferroic/magnetoelectric films
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.85.+t Magnetoelectric effects, multiferroics

Quantitative investigation of magnetic domains with in-plane and out-of-plane easy axes in GaMnAs films by Hall effect

Sangyeop Lee, Hakjoon Lee, Taehee Yoo, Sanghoon Lee, X. Liu, and J. K. Furdyna

J. Appl. Phys. 113, 17C706 (2013); http://dx.doi.org/10.1063/1.4794283 (3 pages)

Online Publication Date: 5 March 2013

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Magnetic anisotropy of ferromagnetic semiconductor GaMnAs film with a low Mn concentration grown on a (001) GaAs substrate was investigated by Hall effect measurements. The presence of domains with in-plane and out-of-plane easy axes was identified in the film by analyzing hysteresis loops observed via the Hall resistance measured in various geometries. Quantitative analysis of the planar Hall resistance showed that the fraction of the sample with magnetic domains having a dominant out-of-plane easy axis was about 6 times larger than the fraction corresponding to domains with easy axis in the sample plane.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.30.Gw Magnetic anisotropy
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ch Domain walls and domain structure
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Strong magnetoelectric coupling in hexaferrites at room temperature

Khabat Ebnabbasi, Marjan Mohebbi, and Carmine Vittoria

J. Appl. Phys. 113, 17C707 (2013); http://dx.doi.org/10.1063/1.4794745 (3 pages) | Cited 1 time

Online Publication Date: 7 March 2013

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In this paper, the magnetoelectric effect in single-crystalline Sr Z-type hexaferrite materials is reported. The measurements include material characterization and change in remanence magnetization (Mr) versus electric field. In a very low electric field equal to 3.75 V/cm, 14% change in Mr was observed. We deduced a magneto-electric coupling of 55.4 in CGS units or 2.32 × 10−6 sm−1 (SI units) which is the highest value measured to date.
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75.85.+t Magnetoelectric effects, multiferroics
75.50.Gg Ferrimagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

The manipulation of magnetic properties by resistive switching effect in CeO2/La0.7(Sr0.1Ca0.9)0.3MnO3 system

X. G. Chen, J. B. Fu, C. Yun, Y. B. Yang, S. Q. Liu, C. S. Wang, H. L. Du, J. Z. Han, Y. C. Yang, and J. B. Yang

J. Appl. Phys. 113, 17C708 (2013); http://dx.doi.org/10.1063/1.4795214 (3 pages)

Online Publication Date: 13 March 2013

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The bipolar resistance switching behavior was observed in the epitaxially grown CeO2/La0.7(Sr0.1Ca0.9)0.3MnO3 (CeO2/LSCMO) heterojunctions on SrTiO3 substrate using pulsed laser deposition technology. It was found that the magnetization of CeO2/LSCMO heterojunction varies with the resistance state of the device when the external triggered voltage is higher than the set and reset voltages. The magnetization could be reversibly changed by exerting external set and reset voltages on the junction. The electron tunneling accompanied by a trapping/detrapping process at the interface is likely responsible for the modulation of the magnetization in this insulator/manganite device.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.15.Fg Pulsed laser ablation deposition
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Heterojunction of multiferroic HoMnO3 on Nb-doped SrTiO3

T. C. Han, C. T. Chen, S. S. Pan, and J. G. Lin

J. Appl. Phys. 113, 17C709 (2013); http://dx.doi.org/10.1063/1.4795218 (3 pages)

Online Publication Date: 13 March 2013

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Orthorhombic HoMnO3 thin films with a-axis orientation are epitaxial grown on Nb-doped SrTiO3(110) substrate using pulsed laser deposition technique to fabricate all-oxide p-n heterojunctions. The structural, magnetic, and electrical properties of heterostructures are measured. The temperature-dependent current-voltage data from 320 to 60 K display diode-like rectifying characteristics in the as-prepared p-n junction. Furthermore, an anomalous increase in the reverse-bias current with decreasing temperature below 240 K is observed. Further analysis suggests that this anomalous electrical transport behavior could be ascribed to the Fowler-Nordheim tunneling through the junctions.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.15.Fg Pulsed laser ablation deposition
68.35.Ct Interface structure and roughness
73.40.Ei Rectification
73.40.Gk Tunneling

First observation of magnetoelectric effect in M-type hexaferrite thin films

Marjan Mohebbi, Khabat Ebnabbasi, and Carmine Vittoria

J. Appl. Phys. 113, 17C710 (2013); http://dx.doi.org/10.1063/1.4795721 (3 pages)

Online Publication Date: 18 March 2013

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The magnetoelectric (ME) effect in M-type hexaferrite thin films is reported. Prior to this work, the ME effect in hexaferrite materials was observed only in bulk polycrystalline materials. Thin films of SrCo2Ti2Fe8O19 were grown on sapphire (0001) using pulsed laser deposition. The thin films were characterized by X-ray diffractometer, scanning electron microscope, energy-dispersive spectroscopy, vibrating sample magnetometer, and ferromagnetic resonance. We measured saturation magnetization of 1250 G, g-factor of 2.66, and coercive field of 20 Oe for these magnetoelectric M-type hexaferrite thin films. The magnetoelectric effect was confirmed by monitoring the change rate in remanence magnetization with the application of DC voltage at room temperature and it gave rise to changes in remanence in the order of 12.8% with the application of only 1 V (DC voltage). We deduced a magnetoelectric coupling, α, of 6.07 × 10−9 s m–1 in SrCo2Ti2Fe8O19 thin films.
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75.70.Ak Magnetic properties of monolayers and thin films
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
75.85.+t Magnetoelectric effects, multiferroics
75.50.Gg Ferrimagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Interface-controlled magnetism and transport of ultrathin manganite films

O. Shapoval, S. Hühn, J. Verbeeck, M. Jungbauer, A. Belenchuk, and V. Moshnyaga

J. Appl. Phys. 113, 17C711 (2013); http://dx.doi.org/10.1063/1.4795422 (3 pages)

Online Publication Date: 19 March 2013

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We report ferromagnetic, TC = 240 K, and metallic, TMI = 250 K, behaviors of a three unit cell thick interface engineered lanthanum manganite film, grown by metalorganic aerosol deposition technique on SrTiO3(100) substrates. Atomically resolved electron microscopy and chemical analysis show that ultrathin manganite films start to grow with La-O layer on a strongly Mn/Ti-intermixed interface, engineered by an additional deposition of 2 u.c. of Sr-Mn-O. Such interface engineering results in a hole-doped manganite layer and stabilizes ferromagnetism and metallic conductivity down to the thickness of d = 3 u.c. The films with d = 8 u.c. demonstrate a bulk-like transport behavior with TMI ∼ TC = 310−330 K.
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75.70.Ak Magnetic properties of monolayers and thin films
79.20.Uv Electron energy loss spectroscopy
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.jd Thickness
73.61.Ng Insulators
75.50.Dd Nonmetallic ferromagnetic materials

Electric field modulation of magnetism and electric properties in La-Ca-MnO3/Pb(Zr0.52Ti0.48)O3 magnetoelectric laminate

Shuiyuan Chen, Huiqin Zhang, Fengjin Liu, Qingying Ye, Lei Tang, Zhigao Huang, and Dunhui Wang

J. Appl. Phys. 113, 17C712 (2013); http://dx.doi.org/10.1063/1.4795871 (3 pages)

Online Publication Date: 21 March 2013

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We investigated the effects of electric field on the magnetization and electric transport properties in La0.6Ca0.4MnO3/Pb(Zr0.52Ti0.48)O3 (LCMO/PZT) thin film prepared by sol-gel method and simple spin coating technology. Obvious converse magnetoelectric effect (the relative change in magnetization, ΔM ∼ 15%), as well as large electroresistance effect (the relative change in resistance, ER ∼ 61%), has been obtained in LCMO thin film with applying electric field on the PZT ceramic. The efficient mechanical coupling, which originated from ferroelectric polarization and inverse piezoelectric effect in PZT substrate, leads to large changes in the magnetism and resistance of LCMO thin film. The experimental results can be interpreted by the changes of both spin exchange coupling and electron-lattice coupling strengths in LCMO film, which result from the strain at the ferromagnetic/ferroelectric interface.
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73.61.Ng Insulators
77.55.H- Piezoelectric and electrostrictive films
75.85.+t Magnetoelectric effects, multiferroics
77.55.Nv Multiferroic/magnetoelectric films
75.70.Ak Magnetic properties of monolayers and thin films
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)

Electric field driven variation in magnetoresistance of Co/Cu/Fe/BaTiO3 heterostructure

Hidekazu Kojima, Tomoyuki Naito, Hironobu Muraoka, Eiji Wada, Ippei Suzuki, Yasuhiro Shirahata, Mitsuru Itoh, and Tomoyasu Taniyama

J. Appl. Phys. 113, 17C713 (2013); http://dx.doi.org/10.1063/1.4795819 (3 pages)

Online Publication Date: 21 March 2013

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We demonstrate control of the magnetoresistance of Co/Cu/Fe giant magnetoresistance structures on BaTiO3(001) by electric field. The magnetoresistance clearly increases with electric field strength in the three different ferroelectric phases of BaTiO3, while the electric field dependence is more significant in the orthorhombic and rhombohedral phases with hysteretic behaviors, associated with the different ferroelectric domain reversal processes of BaTiO3. The results clearly show that electrically induced lattice distortion at the Fe/BaTiO3 interface can provide an alternative means to manipulating the electronic structure of the Fe layer by electric field.
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75.47.De Giant magnetoresistance
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
77.80.Dj Domain structure; hysteresis
73.40.Ns Metal-nonmetal contacts

Comparison of anistropic interface magnetoresistance in Co/Pt and Co/Pd multilayers

Jung-Chuan Lee, Chih-Hsun Hsieh, Che-Chun Chang, Leng-Wei Huang, Lu-Kuei Lin, and Shang-Fan Lee

J. Appl. Phys. 113, 17C714 (2013); http://dx.doi.org/10.1063/1.4795799 (3 pages) | Cited 1 time

Online Publication Date: 22 March 2013

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We fabricate Co/Pt and Co/Pd multilayers and measure magnetoresistance. Our data show clear anisotropic interface magnetoresistance (AIMR) effect, in which the resistance variation shows a different sign from Co films when external magnetic saturation fields are rotated from in-plane transverse to perpendicular direction of the film plane. The AIMR percentages increase with decreasing Co thickness for both multilayers when the Co thickness is larger than 2.5 nm. However, the AIMR decreases in Co/Pt for thinner Co but still increases in Co/Pd, thus, showing inverse dependence to Co thickness.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.30.Gw Magnetic anisotropy

Induced magneto-electric coupling at ferroelectric/ferromagnetic interface

Jeffrey Carvell, Ruihua Cheng, and Q. Yang

J. Appl. Phys. 113, 17C715 (2013); http://dx.doi.org/10.1063/1.4794873 (3 pages)

Online Publication Date: 25 March 2013

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We have demonstrated that at room temperature the electric polarization of a ferroelectric polymer, polyvinylidene fluoride (PVDF), in an artificial multiferroic structure can be controlled by applying an external magnetic field. We found that as the applied magnetic field is changed, the switching of electric polarization for the PVDF depends on the external magnetic field. We also noticed that both the electric coercivity and polarization of the PVDF polymer display hysteretic features as the applied magnetic field is changed. We found that the thickness of the PVDF layer has an effect on the magnetoelectric coupling strength in our samples. The coupling sensitivity increases as the PVDF layer thickness increases. It is possible to control the ferroelectric properties of a PVDF film by tuning the external magnetic field.
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75.85.+t Magnetoelectric effects, multiferroics
77.55.Nv Multiferroic/magnetoelectric films
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
77.80.Dj Domain structure; hysteresis
77.84.Jd Polymers; organic compounds

Strain induced tunable anisotropic magnetoresistance in La0.67Ca0.33MnO3/BaTiO3 heterostructures

Yali Xie, Huali Yang, Yiwei Liu, Zhihuan Yang, Bin Chen, Zhenghu Zuo, Sadhana Katlakunta, Qingfeng Zhan, and Run-Wei Li

J. Appl. Phys. 113, 17C716 (2013); http://dx.doi.org/10.1063/1.4795841 (3 pages)

Online Publication Date: 25 March 2013

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In this paper, we investigated the influence of strain on anisotropic magnetoresistance (AMR) in La0.67Ca0.33MnO3 (LCMO) films epitaxially grown on BaTiO3(001). For 250-nm-thick LCMO film, the AMR shows a peak near the metal-insulator transition (MIT) temperature, which is similar to that in bulk LCMO. When the thickness of LCMO is decreased to 150 nm, the AMR value achieves a maximum at low temperature. For 80-nm-thick LCMO film, in addition to the appearance of the maximum AMR at low temperature, the symmetry and sign of AMR are also changed, associated with interface strain in the different phases of BaTiO3. In comparison, the AMR for the reference LCMO films grown on SrTiO3(001) shows a maximum value near the MIT temperature regardless of the thickness of film. Our experiment results suggest that not only the strain value but also the distortion type can considerably tune the AMR of LCMO films.
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72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
71.30.+h Metal-insulator transitions and other electronic transitions
72.60.+g Mixed conductivity and conductivity transitions
75.47.Lx Magnetic oxides

The anomalous Hall effect in the perpendicular Ta/CoFeB/MgO thin films

S. B. Wu, T. Zhu, X. F. Yang, and S. Chen

J. Appl. Phys. 113, 17C717 (2013); http://dx.doi.org/10.1063/1.4796192 (3 pages)

Online Publication Date: 25 March 2013

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The anomalous Hall effect (AHE) in the perpendicular Ta/CoFeB/MgO thin film has been investigated. Between the AHE coefficient (RS) and longitudinal resistivity (ρxx), a linear behavior of RS/ρxx versus ρxx can be found. Moreover, the conductivity of the film is about 5 × 103 S/cm, which suggests that AHE in the Ta/CoFeB/MgO film be dominated by the intrinsic or scattering-independent mechanism.
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73.40.Ns Metal-nonmetal contacts
73.61.-r Electrical properties of specific thin films
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Point contact Andreev reflection from semimetallic bismuth—The roles of the minority carriers and the large spin-orbit coupling

P. Stamenov

J. Appl. Phys. 113, 17C718 (2013); http://dx.doi.org/10.1063/1.4796049 (3 pages)

Online Publication Date: 27 March 2013

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The Point Contact Andreev Reflection (PCAR) technique has been traditionally and predominantly applied to either the characterisation of superconductors or of spin-polarised metals. The sufficiently large and slowly varying, on the scale of tens of meV around the Fermi level (EF), Density of States (DOS) in metals and highly degenerate semiconductors significantly simplifies the interpretation and quantitative analysis of the measured Differential Conductance Spectra (DCS). Semimetals in general, and particularly the heavy semimetals, because of the presence of several carrier bands and the larger Spin-Orbit coupling, exhibit significantly higher variations in the DOS, close to EF, which can be observed and evaluated with PCAR. Here, DCS of bismuth/niobium point contacts are examined to reveal the relative energy offsets [0.12(3), 2.32(5), and 5.7(2)] meV and the approximate relative DOS contributions of the three main carrier bands (16:5:4). Apart from the bulk, some surface states are also expected to contribute to the observed DOS and be potentially spin-split. The spin polarisation due to all conducting states is evaluated at P ≤ 0.09(7).
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74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
72.25.-b Spin polarized transport

Stress-mediated magnetoelectric memory effect with uni-axial TbCo2/FeCo multilayer on 011-cut PMN-PT ferroelectric relaxor

Yannick Dusch, Nicolas Tiercelin, Alexey Klimov, Stefano Giordano, Vladimir Preobrazhensky, and Philippe Pernod

J. Appl. Phys. 113, 17C719 (2013); http://dx.doi.org/10.1063/1.4795440 (3 pages)

Online Publication Date: 28 March 2013

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We present here the implementation of a magnetoelectric memory with a voltage driven writing method using a ferroelectric relaxor substrate. The memory point consists of a magnetoelastic element in which two orthogonal stable magnetic states are defined by combining uni-axial anisotropy together with a magnetic polarization in the hard axis direction. Using a ferroelectric relaxor substrate, an anisotropic stress is created in the magnetic element when applying a voltage across electrodes. Because of the inverse magnetostrictive effect, the effective anisotropy of the magnetic element is controlled by the applied voltage and used to switch magnetization from one state to the other.
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75.85.+t Magnetoelectric effects, multiferroics
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.80.+q Magnetomechanical effects, magnetostriction

Thermal degradation study of (Fe-Co)-(Mg-F) nanogranular tunneling magnetoresistance films by Mössbauer spectroscopy

S. Koyama, J. Totsuka, N. Kobayashi, and T. Goto

J. Appl. Phys. 113, 17C720 (2013); http://dx.doi.org/10.1063/1.4798279 (3 pages)

Online Publication Date: 3 April 2013

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The effect of heat treatment on the tunneling magnetoresistance (TMR), and microscopic magnetic state of insulating (Fe-Co)-(Mg-F) granular films were studied. The magnetoresistance (MR) ratio at 10 kOe increases with increasing annealing-temperature and the highest MR ratio of 13.5% was obtained for the film annealed at 195 °C for 60 min (optimum-annealed film). Moreover, the MR ratio vs. field (H) curve of the optimum-annealed film shows a sharper variation around zero fields, in comparison with the curve of as-deposition film. However, the MR ratio decreased by further annealing. The Mössbauer spectrum of the as-deposition film shows a singlet spectrum, which suggests that Fe-Co granules are in superparamagnetic state. The film annealed at 195 °C also shows a singlet spectrum but the line width is fairly broad as compared to that of as-deposition film. The Mössbauer spectra change from singlet to sextet after further annealing. Characteristic feature of the spectra was explained by a simple relaxation model and the diameters (d) deduced from the relaxation times are d = 5.4 nm, 5.7 nm, and 6.0 nm for as-deposition film, optimum-annealed film, and further-annealed film, respectively. It is expected that there exists an approximate Fe-Co granule size suitable for TMR sensor.
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81.40.Gh Other heat and thermomechanical treatments
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.47.Pq Other materials
75.50.Tt Fine-particle systems; nanocrystalline materials
75.70.Ak Magnetic properties of monolayers and thin films
76.80.+y Mössbauer effect; other γ-ray spectroscopy

Magnetic properties of MgO-[Co/Pt] multilayers with a CoFeB insertion layer

S. Ishikawa, H. Sato, M. Yamanouchi, S. Ikeda, S. Fukami, F. Matsukura, and H. Ohno

J. Appl. Phys. 113, 17C721 (2013); http://dx.doi.org/10.1063/1.4798499 (3 pages)

Online Publication Date: 3 April 2013

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Magnetic properties of MgO-[Co/Pt] multilayers with a CoFeB insertion layer were investigated and the structure was adopted as a recording layer in magnetic tunnel junctions (MTJs) with perpendicular magnetic easy-axis to attain a high thermal stability. Perpendicular easy-axis was obtained with the Pt thickness range of 0.6–1.2 nm and the CoFeB thickness range of 0.6–1.5 nm. As-made MTJs employing the CoFeB-[Co/Pt] multilayer structure as a recording layer showed tunnel magnetoresistance of 40% on average. A high thermal stability factor over 200 was obtained in the MTJs with the size of 25 nm in diameter.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.-m Magnetotransport phenomena; materials for magnetotransport
75.50.Ss Magnetic recording materials

Anisotropic magnetoresistance in epitaxial La0.67(Ca1−xSrx)0.33MnO3 films

Yiwei Liu, Zhihuan Yang, Huali Yang, Yali Xie, Sadhana Katlakunta, Bin Chen, Qingfeng Zhan, and Run-Wei Li

J. Appl. Phys. 113, 17C722 (2013); http://dx.doi.org/10.1063/1.4798798 (3 pages)

Online Publication Date: 3 April 2013

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We investigated the anisotropic magnetoresistance (AMR) effects for La0.67(Ca1−xSrx)0.33MnO3 films epitaxially grown on (001) oriented SrTiO3 substrates. The increase of Sr doping gives rise to the enhancement of the metal-insulator transition temperature, but suppresses the AMR amplitude. The dependence of AMR on the magnetic field orientation for the Sr doping samples shows the coexistence of two-fold and four-fold symmetries, which is changed with varying the temperature. Moreover, the sign of AMR is changed from negative to positive with increasing the temperature. The abnormal AMR behaviors can be understood by different s-d scattering occurring at different temperatures.
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75.47.Lx Magnetic oxides
75.70.Ak Magnetic properties of monolayers and thin films
85.40.Ry Impurity doping, diffusion and ion implantation technology
71.30.+h Metal-insulator transitions and other electronic transitions
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Magnetic and transport properties of tetragonal- or cubic-Heusler-type Co-substituted Mn-Ga epitaxial thin films

T. Kubota, S. Ouardi, S. Mizukami, G. H. Fecher, C. Felser, Y. Ando, and T. Miyazaki

J. Appl. Phys. 113, 17C723 (2013); http://dx.doi.org/10.1063/1.4799143 (3 pages)

Online Publication Date: 3 April 2013

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The composition dependence of the structural, magnetic, and transport properties of epitaxially grown Mn-Co-Ga films were investigated. The crystal structure was observed to change from tetragonal to cubic as the Co content was increased. In terms of the dependence of saturation magnetization on the Co content, relatively small value was obtained for the Mn2.3Co0.4Ga1.3 film at a large Ku value of 9.2 Merg/cm3. Electrical resistivity of Mn-Co-Ga films was larger than that of pure Mn-Ga film. The maximum value of the resistivity was 490 μΩcm for Mn2.2Co0.6Ga1.2 film. The high resistivity of Mn-Co-Ga might be due to the presence of localized electron states in the films due to chemical disordering caused by the Co substitution.
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75.70.Ak Magnetic properties of monolayers and thin films
68.55.aj Insulators
73.61.At Metal and metallic alloys
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Investigation of anomalous magnetoresistance in topological insulator Bi2Te3 at the onset of superconductivity in indium contacts

J. A. Hagmann, X. Liu, M. Dobrowolska, and J. K. Furdyna

J. Appl. Phys. 113, 17C724 (2013); http://dx.doi.org/10.1063/1.4798482 (3 pages)

Online Publication Date: 4 April 2013

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Presented here is evidence that suggests induced superconductivity in topological insulator Bi2Te3 occurring at its interface with indium (In) contacts. Thin Bi2Te3 films of several thicknesses were grown by molecular beam epitaxy and were studied by magnetotransport measurements using In as contacts. Magnetotransport measurements at temperatures below the superconducting transition of In reveal an anomalous abrupt drop in resistance of the Bi2Te3 samples suggesting the formation of a superconducting region at the In/Bi2Te3 interface induced by the In contacts.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.78.-w Superconducting films and low-dimensional structures
75.70.Ak Magnetic properties of monolayers and thin films
68.55.aj Insulators
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Exchange biased magnetoelectric composites for vector field magnetometers

Enno Lage, Frederik Woltering, Eckhard Quandt, and Dirk Meyners

J. Appl. Phys. 113, 17C725 (2013); http://dx.doi.org/10.1063/1.4798791 (3 pages)

Online Publication Date: 4 April 2013

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Magnetoelectric (ME) vector field sensors can be realized by combining individual sensors with anisotropic sensitivity. Following this approach, exchange biased ME thin film composites were incorporated into two dimensional vector magnetometers. These self biased composites do not need magnetic dc bias fields for their operation, which allows a high degree of miniaturization since interference of individual bias fields is avoided. The successful detection of a two dimensional magnetic vector field opens the path to full three dimensional vector sensing.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
75.85.+t Magnetoelectric effects, multiferroics
07.55.Ge Magnetometers for magnetic field measurements
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
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