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28 May 2012

Volume 100, Issue 22, Articles (22xxxx)

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Appl. Phys. Lett. 100, 222402 (2012); http://dx.doi.org/10.1063/1.3700809 (4 pages)

Felix Balhorn, Simon Jeni, Wolfgang Hansen, Detlef Heitmann, and Stefan Mendach
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Spinel oxides: Δ1 spin-filter barrier for a class of magnetic tunnel junctions

Jia Zhang, X.-G. Zhang, and X. F. Han

Appl. Phys. Lett. 100, 222401 (2012); http://dx.doi.org/10.1063/1.4722804 (4 pages) | Cited 3 times

Online Publication Date: 29 May 2012

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The orbital composition of the electrode wave functions and the complex bands within the barrier band gap are two important factors in deciding the spin-filter effect. This is illustrated in a class of spinel oxides, including MgAl2O4, ZnAl2O4, SiMg2O4, and SiZn2O4. Through first-principles calculations of the complex bands and electron transmission along the [001] direction, they are shown to have the same Δ1 spin-filter effect as MgO due to the combination of both factors. Due to better lattice match with typical bcc magnetic electrodes than MgO, these materials provide a broad spectrum of candidate materials for magnetic tunnel junctions.
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73.40.Rw Metal-insulator-metal structures
71.15.-m Methods of electronic structure calculations

Axial and azimuthal spin-wave eigenmodes in rolled-up permalloy stripes

Felix Balhorn, Simon Jeni, Wolfgang Hansen, Detlef Heitmann, and Stefan Mendach

Appl. Phys. Lett. 100, 222402 (2012); http://dx.doi.org/10.1063/1.3700809 (4 pages) | Cited 1 time

Online Publication Date: 29 May 2012

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We experimentally realized rolled-up permalloy stripes to form three-dimensional ring-like ferromagnetic structures. By means of microwave absorption spectroscopy, we find multiple resonances occurring above a demagnetization field threshold which depends on the ring’s axial width. Our experimental data can be well modeled by assuming both axial and azimuthal spin-wave confinement.
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75.30.Ds Spin waves
75.50.Bb Fe and its alloys
78.70.Gq Microwave and radio-frequency interactions
75.60.-d Domain effects, magnetization curves, and hysteresis

Enhancement of the magneto-optical properties in 2-dimensional bilayered magnetic anti-dot lattice

N. G. Deshpande, J. S. Hwang, K. W. Kim, J. Y. Rhee, Y. H. Kim, L. Y. Chen, and Y. P. Lee

Appl. Phys. Lett. 100, 222403 (2012); http://dx.doi.org/10.1063/1.4722926 (4 pages)

Online Publication Date: 29 May 2012

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The magneto-optical (MO) properties of two-dimensional bilayered magnetic anti-dot lattice (BMAL) structure, which consists of upper perforated “Co” layer over uniform “Ni” underlayer in square-lattice arrangement, were investigated. Enhancement in the MO activity was found in such structures. Nearly 4 times larger MO-Kerr activity was observed for the first-order diffracted beam as compared with that of the zeroth-order one. To understand the origin of the enhanced MO rotation, the magnetization-domain configuration was also investigated by field-dependent magnetic-force microscopy. Additionally, comparison between MO response and magnetization-domain configuration for the rhomboid BMAL structure was done, which allowed us to understand more clearly the enhancement of MO properties.
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78.20.Ls Magneto-optical effects
68.65.Hb Quantum dots (patterned in quantum wells)
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.70.Kw Domain structure (including magnetic bubbles and vortices)
78.67.Hc Quantum dots
78.20.Ek Optical activity

Large magnetocaloric effect induced by intrinsic structural transition in Dy1−x HoxMnO3

Mingjie Shao, Shixun Cao, Shujuan Yuan, Jin Shang, Baojuan Kang, Bo Lu, and Jincang Zhang

Appl. Phys. Lett. 100, 222404 (2012); http://dx.doi.org/10.1063/1.4722930 (4 pages)

Online Publication Date: 29 May 2012

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We report the magnetic and magnetocaloric properties of Dy1−xHoxMnO3 (0 ≤ x ≤ 1). Large entropy change of 12.5 J/kg K and refrigeration capacity of 312 J/kg at 7 T for HoMnO3 is calculated based on isothermal magnetization measurements. The peak temperature of magnetic entropy change for all samples keeps the same 10.5 K, indicating that Ho3+ doping only affects the value of magnetic entropy. An unambiguous intrinsic structural transition near 7 K is first observed by strain measurement, which is believed as the origin of magnetic symmetry transition of Dy1−xHoxMnO3 and induces the magnetocaloric effect with the cooperation interaction between Dy3+/Ho3+and Mn3+ spins.
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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.)
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.K- Solid-solid transitions
61.72.up Other materials
65.40.gd Entropy

Stroboscopic imaging of an alternating magnetic field from a perpendicular magnetic recording head by frequency-modulated magnetic force microscopy

Zhenghua Li, Kodai Hatakeyama, Genta Egawa, Satoru Yoshimura, and Hitoshi Saito

Appl. Phys. Lett. 100, 222405 (2012); http://dx.doi.org/10.1063/1.4720508 (4 pages) | Cited 1 time

Online Publication Date: 29 May 2012

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The alternating current (ac) magnetic field from perpendicular magnetic recording head was imaged by using our developed frequency-modulated magnetic force microscopy (FM-MFM), which uses the frequency modulation of cantilever oscillation caused by applying ac magnetic field to a mechanically oscillated cantilever. The amplitude and phase signals (or orthogonal X and Y signals) of the ac magnetic field can be obtained separately by using the FM-MFM technique incorporated with a lock-in amplifier. A signal transformation technique to characterize the AC magnetic field source for frequency modulated magnetic force microscopy was proposed. Two-dimensional vector analysis together with the magnetization vector rotation of the perpendicular recording head was demonstrated using the FM-MFM method combined with the signal transformation algorithm. By taking advantage of this technique, the present method opens a possibility to stroboscopic analyze the AC magnetic field source and gives a very useful feedback for the development of advanced magnetic recording heads.
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85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Ferromagnetism carried by highly delocalized hybrid states in Sc-doped ZnO thin films

Mohammed Benali Kanoun, Souraya Goumri-Said, Aurélien Manchon, and Udo Schwingenschlögl

Appl. Phys. Lett. 100, 222406 (2012); http://dx.doi.org/10.1063/1.4721807 (4 pages) | Cited 1 time

Online Publication Date: 29 May 2012

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We present first-principles results for Sc-doped ZnO thin films. Neighboring Sc atoms in the surface and/or subsurface layers are found to be coupled ferromagnetically, where only two of the possible configurations induce spin polarization. In the first configuration, the polarization is carried by the Sc d states as expected for transition metal doping. However, there is a second configuration which is energetically favorable. It is governed by polarized hybrid states of the Zn s, O p, and Sc d orbitals. Such highly delocalized states can be an important ingredient for understanding the magnetism of doped ZnO thin films.
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75.70.-i Magnetic properties of thin films, surfaces, and interfaces
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.15.-m Methods of electronic structure calculations
72.25.-b Spin polarized transport
75.50.Pp Magnetic semiconductors

Transport and magnetic properties of the Co2MnSi/Al/Co2MnSi trilayer

H. L. Yu, H. B. Zhang, X. F. Jiang, Y. Zheng, and G. W. Yang

Appl. Phys. Lett. 100, 222407 (2012); http://dx.doi.org/10.1063/1.4725513 (4 pages)

Online Publication Date: 30 May 2012

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Using density functional theory and non-equilibrium Green’s function analysis, we studied the interface structure, interface stability, and magnetic and transport properties of the Co2MnSi/Al/Co2MnSi trilayer. It was found that only the CoCo/Al architecture is thermodynamically stable among four interfacial architectures, CoCo/Al, MnSi/Al, MnMn/Al, and SiSi/Al, and the other interface architectures are not accessible within the limits set under thermodynamic equilibrium with other phases. Calculations of the transmission spectrum, conductance, and resistance-area product showed that the Co2MnSi/Al/Co2MnSi trilayer is a promising candidate for the next-generation of recording sensors in ultrahigh-density hard disks.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.65.Ac Multilayers
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
68.35.Ct Interface structure and roughness
72.80.Sk Insulators
71.20.Gj Other metals and alloys

Carrier localization and out of plane anisotropic magnetoresistance in Nd0.55−xSmxSr0.45MnO3 thin films

M. K. Srivastava, A. Kaur, and H. K. Singh

Appl. Phys. Lett. 100, 222408 (2012); http://dx.doi.org/10.1063/1.4722815 (4 pages) | Cited 3 times

Online Publication Date: 30 May 2012

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The impact of carrier localization on the anisotropic magnetoresistance (AMR) has been investigated in Nd0.55−xSmxSr0.45MnO3 (x = 0.00–0.45) thin films. The substitution of smaller Sm3+ cations for larger Nd3+ reduces the average radius of the A-site of the perovskite lattice and enhances size disorder. This quenched disorder results in (1) enhanced Jahn-Teller (J-T) distortion as suggested by decrease in the out of plane lattice constant, (2) stronger carrier localization as evidenced by enhancement in the activation energy of small polaron hopping, (3) decrease in the ferromagnetic (FM) and insulator-metal transition (IMT) temperatures (TC/TIM), (4) sharpening of the IMT, (5) increase in the low field MR, and (6) large enhancement in the AMR. The AMR-T curves of all the films show a maximum just below TIM. The peak AMR measured at small magnetic field of 4.2 kOe increases from −5% for x = 0.00 to −60% for x = 0.45. The enhancement in AMR has been explained in terms of the unquenching of the orbital angular momentum of t2g3 and eg1 configuration and spin fluctuations due to stronger J-T distortion at higher values of x.
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72.20.My Galvanomagnetic and other magnetotransport effects
73.40.Ns Metal-nonmetal contacts
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Dd Nonmetallic ferromagnetic materials
81.40.Gh Other heat and thermomechanical treatments
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Charge-carrier mediated ferromagnetism in Mo-doped In2O3 films

Chang-Yup Park, Chun-Yeol You, Kun-Rok Jeon, and Sung-Chul Shin

Appl. Phys. Lett. 100, 222409 (2012); http://dx.doi.org/10.1063/1.4722928 (4 pages) | Cited 3 times

Online Publication Date: 30 May 2012

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We investigated the correlation between the ferromagnetism and electric resistivity of Mo-doped (3–10 at. %) In2O3 films. We find that the saturation magnetization increases with the Mo concentration until it reaches its maximum at 7 at. % Mo doping (7.1 emu/cm3), after which it rapidly decreases upon higher doping concentration. Interestingly, the resistivity reveals opposite behavior with the Mo concentration, showing a minimum value at 7 at. % Mo doping. According to the temperature-dependent resistivity and the Hall effect measurements, we find that the samples with higher magnetization show metallic behavior with higher electron concentration. Notably, the samples show a linear relationship between the carrier concentration and the degree of magnetization. We believe the ferromagnetism in Mo-doped In2O3 is ascribed to the indirect exchange interaction mediated by the charge carriers.
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73.61.Le Other inorganic semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
61.72.up Other materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors

Thickness dependence of magneto-optical effects in (Ga,Mn)As epitaxial layers

B. Al-Qadi, N. Nishizawa, K. Nishibayashi, M. Kaneko, and H. Munekata

Appl. Phys. Lett. 100, 222410 (2012); http://dx.doi.org/10.1063/1.4724215 (4 pages) | Cited 2 times

Online Publication Date: 31 May 2012

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Rotation angle (θMO) of a linearly polarized light reflected from in-plane, ferromagnetic (Ga,Mn)As layers was measured precisely using a magneto-optical microscope. The θMO value varies non-linearly as a function of (Ga,Mn)As layer thickness d, showing a maximum at d = 50–60 nm. The thickness dependent θMO was analyzed quantitatively with a model based on an interference effect incorporating birefringence and dichroism, and it has been concluded that the contribution of magnetization-vector dependent refractive index, a magnetic birefringence, is responsible for the observed magneto-optical effect. The magnitude of magnetic birefringence appears to be comparable to those of uniaxial birefringence crystals.
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78.20.Ls Magneto-optical effects
78.20.Fm Birefringence
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Nk Insulators
75.70.Ak Magnetic properties of monolayers and thin films

Suppression of the precessional motion of magnetization in a nanostructured synthetic ferrimagnet

Jong Min Lee and Sang Ho Lim

Appl. Phys. Lett. 100, 222411 (2012); http://dx.doi.org/10.1063/1.4724209 (4 pages) | Cited 1 time

Online Publication Date: 1 June 2012

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The suppression of the precessional oscillation of magnetization is investigated in a nanostructured synthetic ferrimagnet. Both the duration and magnitude of an applied magnetic field pulse play an important role in suppressing the precessional motion. This is in contrast to a single magnetic layer, where efficient suppression can be done by controlling the pulse duration only. The reason for this is that the precessional motion of the two magnetizations in the synthetic ferrimagnet is strongly coupled and, at the conditions of current interest, the coupled precessional motion occurs in the optic mode, where the two magnetizations oscillate in opposite directions.
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75.75.-c Magnetic properties of nanostructures
75.78.Cd Micromagnetic simulations
75.50.Gg Ferrimagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Tt Fine-particle systems; nanocrystalline materials
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