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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 Complex Oxides, CMR, and Exchange Bias

Modeling of colossal magnetoresistance in La0.67Ca0.33MnO3/Pr0.67Ca0.33MnO3 superlattices: Comparison with individual (La1−yPry)0.67Ca0.33MnO3 films

S. Hühn, M. Jungbauer, M. Michelmann, F. Massel, F. Koeth, C. Ballani, and V. Moshnyaga

J. Appl. Phys. 113, 17D701 (2013); http://dx.doi.org/10.1063/1.4793711 (3 pages)

Online Publication Date: 27 February 2013

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Colossal magnetoresistance (CMR) and nm-scale electronic inhomogeneity close to the first order phase transition in perovskite manganites, e.g., (La1−yPry)0.67Ca0.33MnO3 still remain a puzzling phenomenon. We experimentally model a metal-insulator phase coexistence by growing a short period (LCMOn/PCMOn)m superlattices (SLs) with the same thickness for both components. CMR effect was studied as a function of the individual layer thickness n = 2–8 and then compared with chemically homogeneous (La1−yPry)0.67Ca0.33MnO3 LPCMO films. We show that SLs can be superimposed in the phase diagram of LPCMO. The results also point out the importance of the nm-scale electronic rather than chemical separation for realization of the CMR effect as well as limits the lowest boundary for the thickness of an individual manganite material to n ∼ 4u.c.
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75.47.Gk Colossal magnetoresistance
75.47.Lx Magnetic oxides
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
73.21.Ac Multilayers

Influence of Ga doping on rare earth moment ordering and ferromagnetic transition in Nd0.7Sr0.3Co1−xGaxO3

Pawan Kumar, D. V. Maheswar Repaka, M. Aparnadevi, T. S. Tripathi, and R. Mahendiran

J. Appl. Phys. 113, 17D702 (2013); http://dx.doi.org/10.1063/1.4793643 (3 pages)

Online Publication Date: 4 March 2013

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We report the impact of dilution of Co sublattice by non-magnetic Ga3+ ion on the magnetic, electrical, and magnetoresistive properties in Nd0.7Sr0.3Co1−xGaxO3 for x = 0–0.12. Field-cooled magnetization of the parent compound (x = 0) shows an anomalous maximum at T* = 54.6 K much below the onset of ferromagnetic transition (TC = 160 K) of the Co sublattice, which is attributed to the polarization of Nd-4f moments antiparallel to the Co-3d sublattice. Both TC and T* shift to low temperature with increasing x and the Nd-4f spin reverses from antiparallel to parallel with increasing strength of the magnetic field. While the value of high field magnetization is not seriously affected by Ga doping, coercive field at 10 K increases dramatically with increasing x. Ga substitution transforms ferromagnetic metallic state into ferromagnetic insulating state for x ≥ 0.03 and decreases the magnitude of magnetoresistance from 6% for x = 0% to 0.5% for x = 0.12.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.47.Lx Magnetic oxides
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Altering the exchange bias in Co90Fe10/(Co,Fe)O bilayers by changing the antiferromagnet's magnetism via interfacial ion-beam bombardment and different single crystalline MgO substrates

C. Shueh, C.-H. Liu, E. Skoropata, T.-H. Wu, J. van Lierop, and K.-W. Lin

J. Appl. Phys. 113, 17D703 (2013); http://dx.doi.org/10.1063/1.4794281 (3 pages)

Online Publication Date: 8 March 2013

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In this study, we investigated the exchange bias (coupling) effects in CoFe/(Co,Fe)O bilayers by using different single crystal substrates of MgO(100) and MgO(110) and Ar ion-beam bombardment on the surface of the bottom antiferromagnet (Co,Fe)O layer before capping with ferromagnet CoFe. In the CoFe/(Co,Fe)O/MgO(110) bilayer, above the irreversibility temperature (Tirr. ∼ 170 K), there was a rapid decrease in M(T) with increasing temperature, unlike the CoFe/(Co,Fe)O/MgO(100) film that showed an increased Tirr. ∼ 300 K and no observable decrease in M(T) above Tirr. The different M vs T zero-field-cooled/field-cooled behavior of the CoFe/(Co,Fe)O bilayers on MgO(100) and MgO(110) indicated that the FM CoFe spin orientations were affected by the different substrates used via exchange coupling to the AF (Co,Fe)O layer altered by MgO.
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75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
75.30.Et Exchange and superexchange interactions
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Setting temperature effect in polycrystalline exchange-biased IrMn/CoFe bilayers

L. E. Fernandez-Outon, M. S. Araújo Filho, R. E. Araújo, J. D. Ardisson, and W. A. A. Macedo

J. Appl. Phys. 113, 17D704 (2013); http://dx.doi.org/10.1063/1.4795211 (3 pages)

Online Publication Date: 13 March 2013

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We study the effect of atomic interdiffusion on the exchange bias of polycrystalline IrMn/(57Fe + CoFe) multilayers due to the thermal setting process of exchange coupling during field annealing. Depth-resolved 57Fe conversion electron Mössbauer spectroscopy was used to quantify atomic interdiffusion. Vibrating sample magnetometry was used to monitor the variation of exchange bias and magnetisation. It was found that interface sharpness is only affected above ∼350 °C. Three different stages for the setting of exchange bias can be inferred from our results. At the lower setting temperatures (up to 350 °C), the effect of field annealing involves alignment of spins and interfacial coupling due to the setting of both antiferromagnetic (AF) bulk and interface without significant interdiffusion. At a second stage (350–450 °C), where AF ordering dominates over diffusion effects, atomic migration and increased setting of AF spins co-exist to produce a peak in exchange bias field and coercivity. On a third stage (>450 °C), severe chemical intermixing reduces significantly the F/AF coupling.
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75.30.Et Exchange and superexchange interactions
75.50.Bb Fe and its alloys
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Mechanisms of the electron paramagnetic resonance line broadening in La1−xCaxMnO3

M. Auslender, E. Rozenberg, A. I. Shames, and Ya. M. Mukovskii

J. Appl. Phys. 113, 17D705 (2013); http://dx.doi.org/10.1063/1.4794139 (3 pages)

Online Publication Date: 14 March 2013

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A complex theoretical approach, summarizing ions-ions, ions-carries, and carriers-lattice couplings, is proposed for modeling and analyzing the electron paramagnetic resonance line broadening in doped manganites. Fitting the above model to the experimental data supports the applicability of our approach. The results obtained on single crystals and ceramics of prototypical La1−xCaxMnO3 system in a wide interval of Ca-dopant concentration (0 ≤ x ≤ 0.7) evidence that depending on x (i.e., on magnetic ground state and carriers' content and mobility) the discussed effect is governed by different mechanisms—mainly ions-ions and/or carriers-lattice spin relaxation.
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76.30.-v Electron paramagnetic resonance and relaxation
61.72.sd Impurity concentration
72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Sk Insulators

Field-induced magnetic phase transition in Pr3+ doped Sm0.5Sr0.5MnO3 manganites

S. K. Giri and T. K. Nath

J. Appl. Phys. 113, 17D706 (2013); http://dx.doi.org/10.1063/1.4794989 (3 pages)

Online Publication Date: 15 March 2013

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Magnetic properties of Pr3+ doped Sm0.5Sr0.5MnO3 manganite with the variation of particle size down to 30 nm have been investigated in detail. We have critically examined the magnetic field (H) dependence of the order of the ferromagnetic (FM) to paramagnetic (PM) phase transition in this Sm0.35Pr0.15Sr0.5MnO3 manganite. It has been shown that all the particle sizes (bulk to nano) exhibit first order FM → PM phase transition under low magnetic field accompanied by magnetization with thermal hysteresis in the field cooled cooling and warming cycle. However, the samples exhibit a second order magnetic phase transition above a critical field HCR. Again with decreasing the particle size, the ferromagnetic transition temperature, the thermal hysteresis width in the magnetizations, and the critical field HCR significantly decrease, which indicate that the ferromagnetism is weakened and the first-order magnetic phase transition is softened. We have also used the Banerjee criteria to distinguish the first-order magnetic phase transition from the second-order one. A detailed analysis of the magnetization measurements of this manganite reveal the disorder-induced softening of the first order phase transition in this phase separated manganite.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Dd Nonmetallic ferromagnetic materials
75.20.Ck Nonmetals
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.20.My Galvanomagnetic and other magnetotransport effects

Influence of interface roughness on the exchange bias of Co/CoO multilayers

J. Wang, T. Sannomiya, J. Shi, and Y. Nakamura

J. Appl. Phys. 113, 17D707 (2013); http://dx.doi.org/10.1063/1.4795437 (3 pages)

Online Publication Date: 19 March 2013

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The effect of interface roughness on the magnetic properties of ferromagnetic/antiferromagnetic multilayer has been studied by comparing the interfaces within identical multilayer (lower vs. upper) or from different Co/CoO multilayers (different deposition sequence). It has been found that for identical multilayer, the upper Co/CoO interfaces grow rougher and show stronger exchange bias than the lower Co/CoO interfaces. Structural analyses indicate that the successive layer deposition gives rise to a cumulative roughness at the upper interface, which affects the magnetic properties of ferromagnetic layer and its coupling to the antiferromagnetic layers. The interface roughness strengthens the interfacial exchange coupling by the increase of defect-generated uncompensated antiferromagnetic spins; such spins form coupling with the spins from Co layer at the interface. Due to the different coupling strength of each Co layer to the neighboring CoO layers, the multilayer showed distinct switching fields during the magnetization reversal process. Our results imply the possibility to control the strength of exchange bias, coercivity, and related magnetic properties by tuning the interface roughness.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.35.Ct Interface structure and roughness
75.30.Et Exchange and superexchange interactions
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Jk Magnetization reversal mechanisms

Signature of exchange bias and spin-glass like phenomena in Fe/CoO nanocomposite

S. P. Pati, A. Roychowdhury, S. Kumar, and D. Das

J. Appl. Phys. 113, 17D708 (2013); http://dx.doi.org/10.1063/1.4795441 (3 pages)

Online Publication Date: 21 March 2013

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Nanocomposite of Fe/CoO having 10 at. wt. % of α-Fe has been prepared by the high energy ball-milling method. The average particle size was estimated to be 15 nm from the results obtained by the rietveld refinement of x-ray diffraction pattern. The presence of exchange coupling at the interface of ferromagnetic and antiferromagnetic components was confirmed from the shift observed in field-cooled (FC) magnetic hysteresis loop. Irreversibility in temperature dependent zero field cooled (ZFC)-FC magnetization at different applied fields indicates the presence of spin-glass like (SGL) phase. Memory effect observed in the temperature dependent dc-magnetization at FC condition confirmed the existence of SGL state. It is argued that polydispersity and defects at the interfaces of nanoparticles are the possible causes of the observed SGL phase.
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75.30.Et Exchange and superexchange interactions
75.50.Lk Spin glasses and other random magnets
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.07.Bc Nanocrystalline materials
75.75.Cd Fabrication of magnetic nanostructures

Exchange bias in La0.7Sr0.3MnO3/SrMnO3/La0.7Sr0.3MnO3 trilayers

M. Jungbauer, S. Hühn, M. Michelmann, E. Goering, and V. Moshnyaga

J. Appl. Phys. 113, 17D709 (2013); http://dx.doi.org/10.1063/1.4798349 (3 pages)

Online Publication Date: 27 March 2013

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Exchange bias (EB) has been observed for all-manganite La0.7Sr0.3MnO3/SrMnO3/La0.7Sr0.3MnO3 trilayers with ferromagnetic La0.7Sr0.3MnO3 and G-type antiferromagnetic SrMnO3 (SMO) layers, grown on (001) SrTiO3 substrates by metalorganic aerosol deposition. The field shift of the magnetic hysteresis loop HE and the coercivity HC decay exponentially with temperature. HE exhibits a global maximum as a function of SMO interlayer thickness at tSMO ≈ 4.5 nm. We argue that EB behaviour can be explained by the interplay of a spinglass state at the interface and theoretically proposed mechanism based on the Dzyaloshinskii-Moriya interaction.
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75.30.Et Exchange and superexchange interactions
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Ee Antiferromagnetics
75.50.Lk Spin glasses and other random magnets
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Thermal hysteresis of interface biased dipolar coupled nanoelements

Ana L. Dantas, Idalmir Queiroz, Jr., Gustavo Reboucas, Maria G. Dias, and A. S. Carriço

J. Appl. Phys. 113, 17D710 (2013); http://dx.doi.org/10.1063/1.4795868 (3 pages)

Online Publication Date: 27 March 2013

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We report a theoretical investigation of thermal hysteresis of a pair of interface biased elliptical iron nanoelements, separated by an ultrathin layer of nonmagnetic material. The thermal hysteresis originates in the strong dipolar interaction, and is tunable by the nature of the low temperature state and the eccentricity of the nanoelements. The width of the thermal hysteresis varies from 500 K to 100 K for lateral dimensions of 125 nm × 65 nm and 145 nm × 65 nm.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.-c Magnetic properties of nanostructures
81.07.Bc Nanocrystalline materials

Effect of the Pt buffer layer on perpendicular exchange bias based on collinear/non-collinear coupling in a Cr2O3/Co3Pt interface

T. Ashida, Y. Sato, T. Nozaki, and M. Sahashi

J. Appl. Phys. 113, 17D711 (2013); http://dx.doi.org/10.1063/1.4797472 (3 pages)

Online Publication Date: 29 March 2013

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In this study, we fabricated a Cr2O3 (0001) film without and with a Pt buffer layer and investigated its effect on perpendicular exchange coupling in a Cr2O3/Co3Pt interface. The results showed that the exchange bias field (μ0Hex) and blocking temperature (TB) of a Cr2O3 film without and with Pt were very different. The Cr2O3 film without Pt had a lower μ0Hex of 176 Oe and a lower TB of 75 K, whereas that with Pt had a higher μ0Hex of 436 Oe and a higher TB of 150 K. We discussed this difference in μ0Hex and TB values based on collinear/non-collinear coupling in a ferromagnetic and antiferromagnetic interface using Meiklejohn and Bean's exchange anisotropy model.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy
75.50.Ee Antiferromagnetics

Effect of Ge and Al substitutions on exchange bias in Ni-Mn-Sb alloy

M. K. Lee, L. S. Xu, V. V. Marchenkov, R. L. Wang, R. J. Chen, S. Guo, C. P. Yang, and J. C. A. Huang

J. Appl. Phys. 113, 17D712 (2013); http://dx.doi.org/10.1063/1.4798372 (3 pages)

Online Publication Date: 2 April 2013

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See Also: Publisher's Note

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Magnetic properties, martensitic transition, and exchange bias in Ni50Mn36Sb14, Ni50Mn36Sb12Ge2, and Ni50Mn36Sb12Al2 alloys have been investigated. The results reveal that the martensitic transition temperatures and blocking temperature shift to low temperature for Ge substitution and shift to high temperature for Al substitution. The exchange bias field decreases/increases in case of Ge/Al substitution below blocking temperature. All the results can be ascribed to the increase/decrease of ferromagnetic interaction.
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81.05.Bx Metals, semimetals, and alloys
81.30.Kf Martensitic transformations
64.70.kd Metals and alloys
75.30.Et Exchange and superexchange interactions
75.50.Cc Other ferromagnetic metals and alloys

NiFe/CoFe/Cu/CoFe/MnIr spin valves studied by ferromagnetic resonance

A. A. Timopheev, N. A. Sobolev, Y. G. Pogorelov, S. A. Bunyaev, J. M. Teixeira, S. Cardoso, P. P. Freitas, and G. N. Kakazei

J. Appl. Phys. 113, 17D713 (2013); http://dx.doi.org/10.1063/1.4798615 (3 pages)

Online Publication Date: 2 April 2013

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Ion-beam deposited (Glass/Ta/NiFe/CoFe/Cu/CoFe/MnIr/Ta) spin valves (SVs) with a Cu-spacer thickness (tCu) varying from 14 to 28 Å have been studied by ferromagnetic resonance (FMR) and magnetoresistance (MR) measurements. With respect to the interlayer coupling strength between the free and fixed ferromagnetic layers, the samples have been divided in those with a weak coupling (for tCu > 16 Å) and a strong coupling regimes (for tCu ≤ 16 Å). The FMR behavior in these two regimes is quite different. For the weakly coupled series, there are two well-defined FMR peaks stemming from the free and fixed layers. Their in-plane angular dependences exhibit 180° and 360° symmetries, respectively. For the strongly coupled SVs, the resonance modes are hybridized and possess features of both layers simultaneously. The main coupling mechanism between the two layers, as concluded from the FMR and MR measurements, is the Néel “orange-peel” magnetostatic interaction, accompanied by a direct exchange due to pinholes in the Cu spacer for tCu < 17 Å.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Perpendicular magnetic anisotropy and perpendicular exchange bias in sputter-deposited CoO/CoPt multilayer

J. Wang, T. Sannomiya, J. Shi, and Y. Nakamura

J. Appl. Phys. 113, 17D714 (2013); http://dx.doi.org/10.1063/1.4798351 (3 pages)

Online Publication Date: 3 April 2013

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The structural and magnetic properties of room-temperature sputter-deposited CoO/CoPt multilayer have been investigated. It was found that the multilayers show strong perpendicular magnetic anisotropy (PMA) at room temperature. Moreover, after perpendicular field cooling below the Néel temperature of CoO layer, the multilayer with antiferromagnet (AF)/ferromagnet (FM) interfaces exhibits perpendicular exchange bias (PEB). And also the PMA of the multilayer is enhanced after field cooling process. This is considered due to the strong interfacial exchange coupling between the CoPt and CoO layers, which is further confirmed from the significantly enhanced perpendicular coercivity. Similar with the reported Co/noble-metal structures, the strong PMA found here also shows clear interface effect. However, with the multilayer structure studied here, the PMA can survive with relative thicker ferromagnetic layer (tFM ∼ 2.3 nm) at as-deposited state. Therefore, the PMA found in AF/FM multilayer could be partially attributed to the interfacial AF-FM exchange coupling. On the other hand, structural characterization results indicate a well-defined layer structure and strong (111) texture for CoPt layers. CoO layer here provides a good seed layer for the growth of textured CoPt layer. As [111] is one of the easy axis for the fcc CoPt, the (111) texture should also benefit the PMA. Such PMA and PEB originating from the interface would give new parameters to control the magnetic properties especially for multilayer systems.
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75.30.Gw Magnetic anisotropy
75.50.Cc Other ferromagnetic metals and alloys
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions

Exchange bias in core-shell iron-iron oxide nanoclusters

M. Kaur, J. S. McCloy, and Y. Qiang

J. Appl. Phys. 113, 17D715 (2013); http://dx.doi.org/10.1063/1.4799522 (3 pages)

Online Publication Date: 3 April 2013

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An exchange bias study has been performed on core-shell iron-iron oxide (Fe-Fe3O4) nanoclusters (NCs) of sizes 11 nm and 14 nm carrying a different core to shell ratio. NCs show complicated behaviors due to competition between interfacial exchange and Zeeman energy in the presence of magnetic field during cooling. These behaviors are accompanied by the evolution of size-dependent cluster structures in the ferromagnetic-core/ferri- or antiferro-magnetic-shell. Smaller clusters have larger coercive field, exchange bias field, and vertical magnetization shift due to the greater contribution from frozen spins of shell/interfaces and magnetic frustration by the defects and voids present at the interface. These smaller clusters thus also show more dramatic changes with the training effect. Both sizes of clusters display an additional anomaly of the upper part of the hysteresis loop at 10 K under low cooling field (0.1 kOe). This anomaly decreases with number of loop cycles with same field, and disappears with large cooling field (>0.1 kOe). It may be caused by the competition between the magnetization reversal and the magnetostatic interactions.
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75.75.-c Magnetic properties of nanostructures
78.20.Ls Magneto-optical effects
61.72.Qq Microscopic defects (voids, inclusions, etc.)
75.60.Jk Magnetization reversal mechanisms
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ee Antiferromagnetics

Photoelectronic behaviors of bilayer ultrathin films manganite-based heterojunctions

W. W. Gao, L. Hu, Y. P. Sun, J. R. Sun, J. Shen, R. J. Chen, Y. F. Chen, and B. G. Shen

J. Appl. Phys. 113, 17D716 (2013); http://dx.doi.org/10.1063/1.4798341 (3 pages)

Online Publication Date: 5 April 2013

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We presented a systematic study on the photoelectronic properties of the La0.67Ba0.33MnO3 (20 nm)/LaMnO3(t)/SrTiO3:0.05 wt. % Nb (LBMO/LMO(t)/STON) junctions with 0 ≤ t ≤ 30 nm. The short-circuit photocurrent (Iph) is found to show a complex dependence on the LMO buffer layer. It undergoes first a sharp drop as the layer thickness of LMO increases from 0 to 3 nm and then, after a rigid turn, a slow decrease for further increase in layer thickness. These results indicate that the coupling between LBMO and STON can be effectively depressed by a LMO layer of 3 nm. The photocurrent is further found to be temperature dependent, increasing monotonically upon cooling, and the maximal growth, occurring in the junction of t = 3 nm, can be as high as 226% when cooled from 320 K to 40 K. Meanwhile, the Iph-t dependences at different temperatures are similar, which is an indication of temperature independence for the diffusion length of the photocarriers. Analysis of the capacitance-voltage relations indicates that the change of interfacial barrier is the reason for the peculiar photoelectronic behavior observed.
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72.40.+w Photoconduction and photovoltaic effects
79.60.Jv Interfaces; heterostructures; nanostructures
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Controlling exchange bias in FeMn with Cu

Dogan Kaya, Pavel N. Lapa, Priyanga Jayathilaka, Hillary Kirby, Casey W. Miller, and Igor V. Roshchin

J. Appl. Phys. 113, 17D717 (2013); http://dx.doi.org/10.1063/1.4798310 (3 pages)

Online Publication Date: 9 April 2013

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To study the effect of non-magnetic layer (Cu) on magnetic properties of antiferromagnetic FeMn, multilayers of Ta(5 nm)/[FeMn(t)/Cu(5 nm)]10/Ta(5 nm), where t is varied in the range of 5–15 nm, are fabricated by a combination of RF and DC magnetron sputter deposition. Magnetization curves for these samples exhibit magnetic hysteresis, and when the samples are cooled in an applied magnetic field, the hysteresis loops are shifted. This shift is attributed to an “intrinsic” exchange bias effect (i.e., it is observed without a separate ferromagnetic layer). Presented temperature and thickness dependences of the coercive field, magnetic moment, and exchange bias field provide insights into the origin and mechanism of the observed intrinsic exchange bias.
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75.30.Et Exchange and superexchange interactions
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Exchange bias between multiferroic HoMnO3 and ferromagnetic SrRuO3 films

T. C. Han and J. G. Lin

J. Appl. Phys. 113, 17D718 (2013); http://dx.doi.org/10.1063/1.4801504 (3 pages)

Online Publication Date: 11 April 2013

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Orthorhombic HoMnO3 (o-HMO) thin films with a-axis orientation are epitaxially grown on ferromagnetic (FM) SrRuO3 (SRO) layers by using pulsed laser deposition. The structural and magnetic properties of o-HMO/SRO heterostructures are measured. The magnetic hysteresis loops of o-HMO/SRO show exchange bias at temperatures below the antiferromagnetic transition temperature of o-HMO. Furthermore, the large exchange bias field up to 815 Oe is observed at 5 K. These results demonstrate that the exchange bias between a FM oxide and the multiferroic o-HMO could be useful for future applications on spintronic devices.
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75.30.Et Exchange and superexchange interactions
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Fg Pulsed laser ablation deposition
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
77.55.Nv Multiferroic/magnetoelectric films

Electrical detection of spin reorientation transition in ferromagnetic La0.4Sm0.3Sr0.3MnO3

M. Aparnadevi and R. Mahendiran

J. Appl. Phys. 113, 17D719 (2013); http://dx.doi.org/10.1063/1.4797471 (3 pages)

Online Publication Date: 12 April 2013

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Field-cooled magnetization of La0.4Sm0.3Sr0.3MnO3 samples shows an anomalous maximum at a temperature T* = 45 K within the ferromagnetic state, which is suggested to spin reorientation transition of the Mn sublattice aided by antiferromagnetic Sm(4f)-Mn(3d) interaction. While dc resistivity does not show any specific feature at T*, ac electrical impedance shows anomalous features at both T* and at the ferromagnetic transition temperature even in the absence of an external magnetic field. Our results indicate that ac electrical transport can be used to detect multiple magnetic phase transitions whose impact on the dc electrical transport is either weak or masked completely.
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75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Ee Antiferromagnetics
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
72.20.My Galvanomagnetic and other magnetotransport effects

Effects of lattice deformation on magnetic properties of electron-doped La0.8Hf0.2MnO3 thin films

Z. P. Wu, Y. C. Jiang, and J. Gao

J. Appl. Phys. 113, 17D720 (2013); http://dx.doi.org/10.1063/1.4801336 (3 pages)

Online Publication Date: 12 April 2013

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The lattice deformation effects on electric and magnetic properties of electron-doped La0.8Hf0.2MnO3 (LHMO) thin films have been systematically investigated. LHMO films with various thicknesses (15 nm, 40 nm, and 80 nm) were grown on (001) SrTiO3 and (001) LaAlO3 substrates, which induces in-plane tensile and compressive biaxial stress, respectively. The metal-insulator phase transition temperature (TP) and magnetoresistance (MR) effect show a strong dependence on film thickness. TP increases with a decrease in thickness and is enhanced as the lattice strain rises, regardless of whether it is tensile or compressive. The maximum MR ratio is suppressed by reduction of the film thickness. These anomalous phenomena may be attributed to the competition between the strain induced modification of the Mn-O bond length and the eg orbital stability.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
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)
75.70.Ak Magnetic properties of monolayers and thin films

Pressure dependence of resistivity and magnetoresistance in Pr-doped La0.7Ca0.3MnO3

H. K. Jani, D. V. Maheswar Repaka, and R. Mahendiran

J. Appl. Phys. 113, 17D721 (2013); http://dx.doi.org/10.1063/1.4800679 (3 pages)

Online Publication Date: 15 April 2013

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We report the effects of magnetic field (μ0H = 0–7 T) and hydrostatic pressure (P = 1 bar to 9.53 kbar) on electrical resistivity in the phase separated manganite La0.3Pr0.4Ca0.3MnO3. The resistivity shows a first-order transition from paramagnetic insulating to ferromagnetic metallic state at a temperature T = TIM in ambient pressure and zero magnetic field. The first-order transition becomes second-order with increasing pressure and/or magnetic field. Both hydrostatic pressure and magnetic field decrease the magnitude resistivity and shift the resistivity peak at T = TIM towards high temperature with different rates (dTIM/dH = 13.5 K/T for P = 1 bar, 8.8 K/T for P = 9.53 kbar, and dTIM/dP ∼ 4.42 K/kbar in zero field). However, the magnitude of the magnetoresistance decreases with increasing pressure. Baroresistance in the absence of magnetic field for ΔP = 9.53 kbar reaches nearly 100% around 150 K. Interestingly, while the resistivity at a constant temperature shows irreversible behaviour upon cycling the direction of magnetic field at ambient pressure, the irreversibility is eliminated under hydrostatic pressure. Our results indicate that pressure eliminates phase separation by converting the paramagnetic polaronic phase into ferromagnetic metallic phase in the vicinity of phase coexistence.
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72.20.My Galvanomagnetic and other magnetotransport effects
75.20.Ck Nonmetals
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.47.Lx Magnetic oxides
75.50.Dd Nonmetallic ferromagnetic materials
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Exchange bias of perpendicularly magnetized [Co/Pt]3/IrMn multilayer on porous anodized alumina

Z. Shi, X. X. Fan, P. He, S. M. Zhou, H. N. Hu, M. Yang, and J. Du

J. Appl. Phys. 113, 17D722 (2013); http://dx.doi.org/10.1063/1.4801785 (3 pages)

Online Publication Date: 16 April 2013

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The exchange bias of [Co/Pt]3/IrMn multilayers deposited on porous anodized alumina oxide template has been investigated. The perpendicular exchange bias has been successfully established on the anodized alumina template and Si substrate. For samples on the anodized alumina templates, a larger exchange field was obtained but smaller coercivity was observed, in comparison with those on flat Si substrate. Unlike conventional observations, the asymmetry of angular dependence of coercive fields of two branches for nanostructured samples is less prominent than that of the continuous samples.
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75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Exchange bias effect in NiMnSb/CrN heterostructures deposited by magnetron sputtering

Harish Sharma Akkera, Rahul Barman, Navjot Kaur, Nitin Choudhary, and Davinder Kaur

J. Appl. Phys. 113, 17D723 (2013); http://dx.doi.org/10.1063/1.4798373 (3 pages)

Online Publication Date: 17 April 2013

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Exchange bias has been studied in various Ni50Mn36.8Sb13.2/CrN heterostructures with different CrN thicknesses (15 nm–80 nm), grown on Si (100) substrate using magnetron sputtering. The shift in hysteresis loop up to 51 Oe from the origin was observed at 10 K for Ni-Mn-Sb film without CrN layer. On the other hand, a significant shifting of hysteresis loop was observed with antiferromagnetic (AFM) CrN layer in Ni50Mn36.8Sb13.2/CrN heterostructure. The exchange coupled 140 nm Ni50Mn36.8Sb13.2/35 nm CrN heterostructure exhibited a relatively large exchange coupling field of 148 Oe at 10 K compared to other films, which may be related to uncompensated and pinned AFM spins at FM-AFM interface and different AFM domain structures for different thicknesses of CrN layer. Further nanoindentation measurements revealed the higher values of hardness and elastic modulus of about 12.7 ± 0.38 GPa and 179.83 ± 1.24 GPa in Ni50Mn36.8Sb13.2/CrN heterostructures making them promising candidate for various multifunctional MEMS devices.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
68.35.Gy Mechanical properties; surface strains
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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