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11 Apr 2011

Volume 98, Issue 15, Articles (15xxxx)

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Appl. Phys. Lett. 98, 153103 (2011); http://dx.doi.org/10.1063/1.3555342 (3 pages)

Hsin-Yu Wu and Brian T. Cunningham
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Large magnetoresistance in current-perpendicular-to-plane pseudospin valve using a Co2Fe(Ge0.5Ga0.5) Heusler alloy

Y. K. Takahashi, A. Srinivasan, B. Varaprasad, A. Rajanikanth, N. Hase, T. M. Nakatani, S. Kasai, T. Furubayashi, and K. Hono

Appl. Phys. Lett. 98, 152501 (2011); http://dx.doi.org/10.1063/1.3576923 (3 pages) | Cited 14 times

Online Publication Date: 11 April 2011

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Using a newly developed highly spin-polarized Heusler alloy, Co2Fe(Ga0.5Ge0.5) (CFGG), as ferromagnetic layers, we have fabricated a current-perpendicular-to-plane pseudospin valve with large resistance change-area product (ΔRA) of 9.5 mΩ μm2 and magnetoresistance (MR) ratio (100×ΔR/R) of 41.7% at 300 K. These values were further enhanced to ΔRA = 26.4 mΩ μm2 and MR = 129.1% at 10 K. The large MR values are attributed to the high spin polarization of the CFGG alloy confirmed by point contact Andreev reflection measurements.
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75.47.Np Metals and alloys
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys
72.25.Ba Spin polarized transport in metals

Engineering of magnetostriction in Fe3Pt1−xIrx by controlling the Ir concentration

Dorj Odkhuu, Won Seok Yun, S. H. Rhim, and Soon Cheol Hong

Appl. Phys. Lett. 98, 152502 (2011); http://dx.doi.org/10.1063/1.3578190 (3 pages) | Cited 1 time

Online Publication Date: 11 April 2011

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A tremendous change in both the sign and magnitude of magnetostriction (λ001) in Fe3Pt1−xIrx (x = 0–1.0) was discovered through a first-principles study using the highly precise full-potential linearized augmented plane wave method. The obtained λ001 values span a wide range from −1050 (x = 0) to +2670 ppm (x = 0.25), a significantly large enhancement over the λ001 values attained for Galfenol, a widely investigated material. Further analysis confirmed that this large effect originates mainly from the nonmagnetic Ir and Pt with induced moments, of which the 5d orbital has larger spin–orbit coupling than the 3d orbital of Fe.
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75.80.+q Magnetomechanical effects, magnetostriction
75.30.Cr Saturation moments and magnetic susceptibilities
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Surface morphology and magnetic anisotropy in (Ga,Mn)As

S. Piano, X. Marti, A. W. Rushforth, K. W. Edmonds, R. P. Campion, M. Wang, O. Caha, T. U. Schülli, V. Holý, and B. L. Gallagher

Appl. Phys. Lett. 98, 152503 (2011); http://dx.doi.org/10.1063/1.3579534 (3 pages) | Cited 2 times

Online Publication Date: 12 April 2011

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Atomic force microscopy and grazing incidence x-ray diffraction measurements have revealed the presence of ripples, aligned along the [1math0] direction on the surface of (Ga,Mn)As layers grown on GaAs(001) substrates and buffer layers, with periodicity of about 50 nm in all samples that have been studied. These samples show the strong symmetry breaking uniaxial magnetic anisotropy normally observed in such materials. We observe a clear correlation between the amplitude of the surface ripples and the strength of the uniaxial magnetic anisotropy component suggesting that these ripples might be the source of such anisotropy.
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75.70.Ak Magnetic properties of monolayers and thin films
75.30.Gw Magnetic anisotropy
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
68.35.bg Semiconductors
68.55.-a Thin film structure and morphology

Magnetic interaction in perpendicular recording media with synthetic nucleation layers

S. N. Piramanayagam, H. K. Tan, M. Ranjbar, S. K. Wong, R. Sbiaa, and T. C. Chong

Appl. Phys. Lett. 98, 152504 (2011); http://dx.doi.org/10.1063/1.3579528 (3 pages) | Cited 1 time

Online Publication Date: 13 April 2011

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Perpendicular recording media, where the CoCrPt-oxide recording layer is deposited on carbon based synthetic nucleation (SN) layers, have been proposed for recording applications and studied using first-order reversal curves for their magnetic interaction behavior. The magnetic properties of media with SN layer show better intergranular segregation whereas the media without SN layer shows otherwise. It is proposed that a dual SN layer structure, where an SN layer deposited above and below the high pressure sputtered Ru layer is suitable for achieving smaller grain size as well as better intergranular segregation.
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75.50.Ss Magnetic recording materials
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)

Surface ferromagnetism in hydrogenated-ZnO film

T. Li, C. S. Ong, T. S. Herng, J. B. Yi, N. N. Bao, J. M. Xue, Y. P. Feng, and J. Ding

Appl. Phys. Lett. 98, 152505 (2011); http://dx.doi.org/10.1063/1.3581046 (3 pages) | Cited 10 times

Online Publication Date: 14 April 2011

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Nonmagnetic ZnO films were found to exhibit room temperature ferromagnetism after hydrogen annealing at elevated temperatures (100–500 °C), accompanied by (OH) bonds detection. The areal saturation magnetization Ms ( ∼ 1.1×10−5 emu cm−2) was insensitive to film thickness, suggesting surface magnetism. The attribution to OH bonds on surface was further supported when the ferromagnetism disappeared after a short immersion for 1 s in acid solution while ferromagnetism was relatively stable in basic environment. The alternative H2- and Ar-annealing can switch ferromagnetic “on” and “off” state, as the annealing under Ar atmosphere can reduce OH bond quantity significantly. First-principles calculations have further confirmed that OH-terminated ZnO surface belonging to the p31m two-dimensional space group has the lowest formation energy of −2.97 eV and a magnetic moment of 0.30 μB per OH due to unpaired magnetic moment of electrons occupying O 2p orbital. Insufficient surface OH concentration may result in antiferromagnetism and/or paramagnetism.
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75.70.Rf Surface magnetism
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Pp Magnetic semiconductors
75.30.Cr Saturation moments and magnetic susceptibilities
75.70.Ak Magnetic properties of monolayers and thin films

Observation of spin-orbital compensation in Sm1−xGdxNi2

Bibekananda Maji, K. G. Suresh, and A. K. Nigam

Appl. Phys. Lett. 98, 152506 (2011); http://dx.doi.org/10.1063/1.3581049 (3 pages)

Online Publication Date: 14 April 2011

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A systematic study of Sm1−xGdxNi2 series shows signatures of perfect spin-orbital compensation at x = 0.03 and 0.035. Magnetization measurements show that both these compounds magnetically order at about 25 K. Below this temperature, the magnetization data shows a compensation point. For x = 0.04 and 0.05, large conduction electron polarization prevents the occurrence of exact compensation. The features seen in this case are found to be quite identical to those of the classical spin-orbit compensated ferromagnet, namely (Sm,Gd)Al2.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Cc Other ferromagnetic metals and alloys
75.25.Dk Orbital, charge, and other orders, including coupling of these orders
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Mirror symmetry in magnetization reversal and coexistence of positive and negative exchange bias in Ni/FeF2

M. Kovylina, M. Erekhinsky, R. Morales, I. K. Schuller, A. Labarta, and X. Batlle

Appl. Phys. Lett. 98, 152507 (2011); http://dx.doi.org/10.1063/1.3577648 (3 pages)

Online Publication Date: 15 April 2011

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Positively and negatively exchange biased (PEB and NEB) magnetoresistance (MR) loops in Ni/FeF2 ferromagnetic/antiferromagnetic (AF) heterostructures proceed through the same reversal mechanisms. The MR curves exhibit mirror symmetry: the increasing (decreasing) field branch of the PEB (NEB) loop is identical to the decreasing (increasing) branch of the NEB (PEB) loop, suggesting that the interfacial areal density of pinned uncompensated AF spins responsible for PEB and NEB is similar. Micromagnetic simulations are in agreement with experimental results and imply the coexistence of EB domains of opposite sign for all cooling fields, which results in a reversal mechanism not previously reported.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Jk Magnetization reversal mechanisms
75.78.Cd Micromagnetic simulations
75.30.Et Exchange and superexchange interactions

Finite-element simulations of hysteretic ac losses in a bilayer superconductor/ferromagnet heterostructure subject to an oscillating transverse magnetic field

Y. A. Genenko, H. Rauh, and P. Krüger

Appl. Phys. Lett. 98, 152508 (2011); http://dx.doi.org/10.1063/1.3560461 (3 pages) | Cited 6 times

Online Publication Date: 15 April 2011

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Numerical simulations of hysteretic ac losses in a bilayer superconductor/ferromagnet heterostructure subject to an oscillating transverse magnetic field are performed within the quasistatic approach, calling upon the ANSYS finite-element software program and exploiting magnetostatic-electrostatic analogs. It is shown that one-sided magnetic shielding of a thin, type-II superconductor strip can lead to an enhancement or, respectively, a reduction of hysteretic ac losses as compared to those for a nonmagnetic support, depending on the amplitude of the applied magnetic field.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.70.-b Superconducting materials other than cuprates
02.60.-x Numerical approximation and analysis
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