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5 May 2008

Volume 92, Issue 18, Articles (18xxxx)

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Appl. Phys. Lett. 92, 182104 (2008); http://dx.doi.org/10.1063/1.2917705 (3 pages)

Jiang Chen, Yibin Hu, Ke Xia, and Zhongshui Ma
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Photoelectric response of Schottky barrier in La0.7Ca0.3MnO3/Nb:SrTiO3 heterojunctions

Z. Luo, J. Gao, A. B. Djurišić, C. T. Yip, and G. B. Zhang

Appl. Phys. Lett. 92, 182501 (2008); http://dx.doi.org/10.1063/1.2920765 (3 pages) | Cited 14 times

Online Publication Date: 6 May 2008

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Heterojunctions composed of La0.7Ca0.3MnO3 and 0.05 wt % Nb-doped SrTiO3 were fabricated using pulse laser deposition. The current-voltage characteristics of such heterojunctions can be described by tunneling with an effective Schottky barrier. These junctions showed significant response to ultraviolet and visible light. Band-to-band and internal photoemission were characterized by photoelectric experiments. A quantum efficiency of about 86% was observed at an incident energy of ∼ 3.95 eV, which corresponds to the band-to-band excitation of electrons in Nb:SrTiO3. From the internal photoemission, the height of Schottky barrier was determined as 1.64 eV.
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72.40.+w Photoconduction and photovoltaic effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling
78.55.Hx Other solid inorganic materials
81.15.Fg Pulsed laser ablation deposition

Antiferromagnetic interlayer exchange coupling between Fe3O4 layers across a nonmagnetic MgO dielectric layer

Han-Chun Wu, S. K. Arora, O. N. Mryasov, and I. V. Shvets

Appl. Phys. Lett. 92, 182502 (2008); http://dx.doi.org/10.1063/1.2919081 (3 pages) | Cited 14 times

Online Publication Date: 7 May 2008

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We have investigated the interlayer exchange coupling between the epitaxial spinel Fe3O4 layers across an insulating nonmagnetic MgO spacer. The epitaxial structure used for these investigations was Fe3O4 (10 nm)/MgO (0.8–3 nm)/Fe3O4 (10 nm)/NiO (15 nm) multilayers grown on MgO (100) substrates. We find that the two Fe3O4 layers are antiferromagnetic coupled through the MgO spacer when the MgO thickness is less than 1.5 nm. Furthermore, ab initio calculation of IEC for Fe/MgO/Fe indicates the importance of electrode states, in particular, partial oxidation of the ferromagnetic electrodes.
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75.30.Et Exchange and superexchange interactions
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
71.15.-m Methods of electronic structure calculations
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Ee Antiferromagnetics

Magnetic coupling between rare-earth and iron atoms in the La1−xRxFe11.5Si1.5 (R = Ce, Pr, and Nd) intermetallics

L. Jia, J. R. Sun, J. Shen, Q. Y. Dong, F. X. Hu, T. Y. Zhao, and B. G. Shen

Appl. Phys. Lett. 92, 182503 (2008); http://dx.doi.org/10.1063/1.2921781 (3 pages) | Cited 7 times

Online Publication Date: 7 May 2008

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A systematic investigation on the effect of R doping, particularly the magnetic coupling between R and Fe, has been performed for the La1−xRxFe11.5Si1.5 intermetallics (R = Ce, Pr, and Nd). A magnetic interaction comparable to that between Fe atoms is found between the R and Fe atoms, which causes an enhancement of the Curie temperature up to ∼ 11% when ∼ 30% of the La atoms are replaced by R. The R–Fe coupling is further found to be strongly dependent of the species of the rare earths. It monotonically grows as R sweeps from Ce to Nd. This could be a consequence of the lanthanide contraction, which causes an enhancement of the intra-atomic magnetic coupling.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
61.72.up Other materials

An easy mechanical way to create ferromagnetic defective ZnO

K. Potzger, Shengqiang Zhou, J. Grenzer, M. Helm, and J. Fassbender

Appl. Phys. Lett. 92, 182504 (2008); http://dx.doi.org/10.1063/1.2921782 (3 pages) | Cited 25 times

Online Publication Date: 7 May 2008

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We present an experiment for the creation of unconventional ferromagnetism in pure ZnO powder by application of mechanical force. The ferromagnetism is related to flakelike structures in planar compressed pieces of the powder with easy axis in the plane. It is associated with defect creation and disappears upon annealing in oxygen. Besides cluster formation, such defects might be one of the nonintrinsic origins of ferromagnetism in transition metal doped ZnO.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
61.72.J- Point defects and defect clusters

Room-temperature-photoinduced magnetism and spin-electronic functions of spinel ferrite with a spin-cluster structure

Teruo Kanki, Yasushi Hotta, Naoki Asakawa, Munetoshi Seki, Hitoshi Tabata, and Tomoji Kawai

Appl. Phys. Lett. 92, 182505 (2008); http://dx.doi.org/10.1063/1.2896609 (3 pages) | Cited 1 time

Online Publication Date: 8 May 2008

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Room-temperature-photoinduced magnetization (PIM) was observed in spinel ferrite Al0.2Ru0.8Fe2O4 thin films with a spin-cluster-glass structure. Additionally, the films exhibited significant properties as spintronic materials, showing a low saturation magnetization under 0.6μB/unit cell and good conductivity with a high spin polarized electron level of over 75%. A combination of high-temperature PIM and the electronic properties associated with spintronics would generate an area of research and development that utilize the degrees of freedom offered by optical systems in the field of spintronics.
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68.55.-a Thin film structure and morphology
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
61.43.Fs Glasses

Large magnetocaloric effect in Sm0.52Sr0.48MnO3 in low magnetic field

P. Sarkar, P. Mandal, and P. Choudhury

Appl. Phys. Lett. 92, 182506 (2008); http://dx.doi.org/10.1063/1.2919732 (3 pages) | Cited 15 times

Online Publication Date: 8 May 2008

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This letter reports on the magnetocaloric properties of Sm0.52Sr0.48MnO3 single crystal. A magnetic field of only 1 T yields a change in the magnetic entropy by 5.9 J/(kg K) at TC ( = 124 K), which is higher than those observed in several other perovskite manganites and rare earth alloys of comparable TC. This change originates from a sharp magnetization jump, associated with a first-order metamagnetic transition. Such a large change in entropy at a low magnetic field makes this material useful for magnetic refrigeration.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Abnormal phase transition and magnetic properties in Cu, Fe co-doped In2O3 nanocrystals

Dewei Chu, Yu-Ping Zeng, and Dongliang Jiang

Appl. Phys. Lett. 92, 182507 (2008); http://dx.doi.org/10.1063/1.2920818 (3 pages) | Cited 8 times

Online Publication Date: 8 May 2008

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Fe, Cu co-doped In2O3 nanocrystals were synthesized by a coprecipitation method. Phase analyses revealed that Fe ions have high solubility (up to 15.4 at. %) in the In2O3 matrix, while the Cu ions strongly restrain In2O3 phase transition from cubic to hexagonal. Raman spectroscopy shows that by adding Cu ions, the defect concentration increases. The samples show no evidence of ferromagnetism by additional Cu doping, indicating that Cu content might be a key point to realize room temperature ferromagnetism in Fe doped In2O3.
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64.70.Nd Structural transitions in nanoscale materials
81.07.Bc Nanocrystalline materials
81.30.Dz Phase diagrams of other materials
81.30.Mh Solid-phase precipitation
61.72.up Other materials
75.50.Dd Nonmetallic ferromagnetic materials

Characterization of strain-induced martensite phase in austenitic stainless steel using a magnetic minor-loop scaling relation

Satoru Kobayashi, Atsushi Saito, Seiki Takahashi, Yasuhiro Kamada, and Hiroaki Kikuchi

Appl. Phys. Lett. 92, 182508 (2008); http://dx.doi.org/10.1063/1.2924305 (3 pages) | Cited 4 times

Online Publication Date: 8 May 2008

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We propose a combined magnetic method using a scaling power-law rule and initial permeability in magnetic minor hysteresis loops for characterization of ferromagnetic α′ martensites in austenitic stainless steel. The scaling power law between the hysteresis loss and remanence is universal, being independent of volume fraction of strain-induced α′ martensites. A coefficient of the power law largely decreases with volume fraction, while the initial permeability linearly increases, reflecting a change in the morphology and quantity of martensites, respectively. The present method is highly effective for integrity assessment of austenitic stainless steels because of the sensitivity and extremely low measurement field.
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81.05.Bx Metals, semimetals, and alloys
81.30.Kf Martensitic transformations
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
64.70.kd Metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetism and clustering in Cu doped ZnO

Dan Huang, Yu-Jun Zhao, Di-Hu Chen, and Yuan-Zhi Shao

Appl. Phys. Lett. 92, 182509 (2008); http://dx.doi.org/10.1063/1.2920572 (3 pages) | Cited 22 times

Online Publication Date: 9 May 2008

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The influence of defect charge state on the magnetism of Cu doped ZnO as well as the Cu defects clustering have been investigated by the first-principles calculations. We demonstrate that p-type ZnO:Cu could have ferromagnetic (FM) property, but n-type ZnO:Cu would not have local magnetic moment. Furthermore, the neutral substitutive Cu defects are found to be favorable in clustering, which maintains the FM ordering.
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75.20.Hr Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions
71.55.Gs II-VI semiconductors
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials

Hydrostatic pressure effect on archetypal Sm0.52Sr0.48MnO3 single crystal

K. Mydeen, P. Sarkar, P. Mandal, A. Murugeswari, C. Q. Jin, and S. Arumugam

Appl. Phys. Lett. 92, 182510 (2008); http://dx.doi.org/10.1063/1.2920762 (3 pages) | Cited 10 times

Online Publication Date: 9 May 2008

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The effect of hydrostatic pressure (P) on the c-axis electrical resistivity (ρc) and ferromagnetic (FM) transition temperature (TC) of Sm0.52Sr0.48MnO3 single crystal has been investigated. At P = 0, the strong hysteretic nature of metal-insulator transition (MIT) and the abrupt decrease of ρc by several orders just below TC suggest that the FM transition is discontinuous in nature. The application of pressure strongly decreases ρc, shifts MIT to higher temperature at the rate of 19 K/GPa, and suppresses the hysteresis width. The nature of the FM phase transition would change from discontinuous to continuous at around P = 2.5 GPa.
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62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
72.60.+g Mixed conductivity and conductivity transitions
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

The crossover from the vortex glass to the Bose glass in nanostructured YBa2Cu3O7−x films

Tomoya Horide, Kaname Matsumoto, Paolo Mele, Ataru Ichinose, Ryusuke Kita, Masashi Mukaida, Yutaka Yoshida, and Shigeru Horii

Appl. Phys. Lett. 92, 182511 (2008); http://dx.doi.org/10.1063/1.2924770 (3 pages) | Cited 8 times

Online Publication Date: 9 May 2008

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The glass-liquid transitions of quantized vortices were studied to understand the vortex behavior in YBa2Cu3O7−x films. We systematically controlled the pinning strength, spatial distribution, and shape of disorders by engineering of nanoinclusions in YBa2Cu3O7−x films. In these disorder systems, we observed the crossover between the vortex glass (VG) and the Bose glass (BG). The increase in pinning strength and ordering of isotropic disorders do not change the critical exponents and the conversion between the BG and the VG is triggered only by the anisotropy of pinning centers.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
64.70.D- Solid-liquid transitions
64.70.P- Glass transitions of specific systems
74.78.Na Mesoscopic and nanoscale systems
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