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7 May 2012

Volume 100, Issue 19, Articles (19xxxx)

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Appl. Phys. Lett. 100, 191901 (2012); http://dx.doi.org/10.1063/1.4709436 (4 pages)

Muamer Kadic, Tiemo Bückmann, Nicolas Stenger, Michael Thiel, and Martin Wegener
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Spin-polarization of VGaON center in GaN and its application in spin qubit

Xiaopeng Wang, Mingwen Zhao, Zhenhai Wang, Xiujie He, Yan Xi, and Shishen Yan

Appl. Phys. Lett. 100, 192401 (2012); http://dx.doi.org/10.1063/1.4712595 (4 pages) | Cited 1 time

Online Publication Date: 7 May 2012

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VGaON center in cubic gallium nitride is a defect complex composing of a substitutional oxygen atom at nitrogen site (ON) and an adjacent gallium vacancy (VGa). Based on first-principles calculations, we predicted that this VGaON center has much in common with the famous nitrogen-vacancy center in diamond, but the excitation energy is very low. The electron spin-polarization of the centers can be tuned by changing the charge states. The neutral ONVGa center has the v↓ and exy↓ states being well isolated from the bulk bands with appropriate spacing which are suitable for achieving spin qubit operation with low excitation energy.
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72.25.Dc Spin polarized transport in semiconductors
61.72.jd Vacancies
61.66.Fn Inorganic compounds
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations
71.20.Nr Semiconductor compounds
71.55.Eq III-V semiconductors

The comparison of direct and indirect methods for determining the magnetocaloric parameters in the Heusler alloy Ni50Mn34.8In14.2B

Igor Dubenko, Tapas Samanta, Abdiel Quetz, Alexander Kazakov, Igor Rodionov, Denis Mettus, Valerii Prudnikov, Shane Stadler, Philip Adams, Joseph Prestigiacomo, Alexander Granovsky, Arcady Zhukov, and Naushad Ali

Appl. Phys. Lett. 100, 192402 (2012); http://dx.doi.org/10.1063/1.4714539 (4 pages) | Cited 2 times

Online Publication Date: 7 May 2012

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The magnetocaloric properties of the Ni50Mn34.8In14.2B Heusler alloy have been studied by direct measurements of the adiabatic temperature change (ΔTAD(T,H)) and indirectly by magnetization (M(T,H)), differential scanning calorimetry, and specific heat (C(T,H)) measurements. The presence of a first-order ferromagnetic-paramagnetic transition has been detected for Ni50Mn34.8In14.2B at 320 K. The magnetocaloric parameters, i.e., the magnetic entropy change (ΔSM = (2.9-3.2) J/kgK) and the adiabatic temperature change (ΔTAD = (1.3-1.52) K), have been evaluated for ΔH = 1.8 T from CP(T,H) and M(T,H) data and from direct ΔTAD(T,H) measurements. The extracted magnetocaloric parameters are comparable to those of Gd.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Generation and annihilation of domain walls in nanowires by localized fields

Falk-Ulrich Stein, Lars Bocklage, Toru Matsuyama, and Guido Meier

Appl. Phys. Lett. 100, 192403 (2012); http://dx.doi.org/10.1063/1.4711222 (3 pages) | Cited 2 times

Online Publication Date: 7 May 2012

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We study the creation and annihilation of domain walls in a permalloy nanowire by local Oersted fields of current pulses passing through a perpendicularly aligned stripline. The occurrence of both processes is investigated for current pulses of different polarities and for various external magnetic fields. Reliable creation and annihilation are achieved for small and zero external fields, while higher externally applied fields lead to the suppression of both processes as well as to the creation of multiple domain walls in the wire.
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75.60.Ch Domain walls and domain structure
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)

Defect and adsorbate induced ferromagnetic spin-order in magnesium oxide nanocrystallites

Ashok Kumar, Jitendra Kumar, and Shashank Priya

Appl. Phys. Lett. 100, 192404 (2012); http://dx.doi.org/10.1063/1.4712058 (4 pages) | Cited 5 times

Online Publication Date: 8 May 2012

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We report the correlation between d0 ferromagnetism, photoluminescence (PL), and adsorbed hydrogen (H−) species in magnesium oxide (MgO) nanocrystallites. Our study suggests that the oxygen vacancies, namely singly ionized anionic vacancies (F+) and dimers (F22+) induce characteristic photoluminescence and the room-temperature ferromagnetic spin-order. Nanocrystallites with low population of oxygen vacancies have revealed diamagnetic behavior. Intriguingly, on adsorption of hydrogen (H−) species in the MgO nanocrystallites, ferromagnetic behavior was either enhanced (in the case of highly oxygen deficient nanocrystallites) or begun to percolate (in the case of nanocrystallite with low population density of oxygen vacancies).
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75.50.Tt Fine-particle systems; nanocrystalline materials
78.55.Hx Other solid inorganic materials
61.72.jd Vacancies
75.75.-c Magnetic properties of nanostructures
75.20.Ck Nonmetals
75.50.Dd Nonmetallic ferromagnetic materials

Antiferromagnetic domain wall engineering in chromium films

J. M. Logan, H. C. Kim, D. Rosenmann, Z. Cai, R. Divan, O. G. Shpyrko, and E. D. Isaacs

Appl. Phys. Lett. 100, 192405 (2012); http://dx.doi.org/10.1063/1.4712598 (4 pages) | Cited 1 time

Online Publication Date: 8 May 2012

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We have engineered an antiferromagnetic domain wall by utilizing a magnetic frustration effect of a thin iron cap layer deposited on a chromium film. Through lithography and wet etching, we selectively remove areas of the Fe cap layer to form a patterned ferromagnetic mask over the Cr film. Removing the Fe locally removes magnetic frustration in user-defined regions of the Cr film. We present x-ray microdiffraction microscopy results confirming the formation of a 90° spin-density wave propagation domain wall in Cr. This domain wall nucleates at the boundary defined by our Fe mask.
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75.60.Ch Domain walls and domain structure
81.65.Cf Surface cleaning, etching, patterning
75.50.Ee Antiferromagnetics
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Ds Spin waves

Magnetic vortices in single crystalline Fe-V disks with four folds magnetic anisotropy

K. Mitsuzuka, D. Lacour, M. Hehn, S. Andrieu, and F. Montaigne

Appl. Phys. Lett. 100, 192406 (2012); http://dx.doi.org/10.1063/1.4711219 (4 pages) | Cited 1 time

Online Publication Date: 8 May 2012

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Magnetic vortices in circular disks made from Fe-V single crystal film have been studied by magnetic force microscopy. At remanent state, all the disks host a single vortex structure. The magnetic contrast differs drastically from the one usually observed in "traditional" materials and reveals the influence of the four folds anisotropy originating from the bcc structure of Fe-V lattice. Field dependence of vortex position has been studied. The vortex displacement is observed to be perpendicular to the field and depends on the field direction. Micromagnetic simulations reproduce quantitatively this behavior and explain the influence of cubic magnetic anisotropy.
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75.70.Ak Magnetic properties of monolayers and thin films
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Beyond ferromagnetic resonance: The inertial regime of the magnetization

E. Olive, Y. Lansac, and J.-E. Wegrowe

Appl. Phys. Lett. 100, 192407 (2012); http://dx.doi.org/10.1063/1.4712056 (4 pages)

Online Publication Date: 9 May 2012

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An inertial regime of the magnetization dynamics at short time scales has been recently predicted for uniform magnetization. We study numerically the corresponding generalized Gilbert equation in both the time domain and in the frequency domain. The time dependence shows a typical nutation behavior that is superimposed to the usual precession of the magnetization around the static magnetic field. In the frequency domain, a second inertial resonance peak at high frequency—added to the usual ferromagnetic Resonance—takes place in the vicinity of the nutation frequency. The typical properties of the inertial resonance are investigated.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.78.Cd Micromagnetic simulations
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Electric field control of domain wall propagation in Pt/Co/GdOx films

Uwe Bauer, Satoru Emori, and Geoffrey S. D. Beach

Appl. Phys. Lett. 100, 192408 (2012); http://dx.doi.org/10.1063/1.4712620 (4 pages) | Cited 7 times

Online Publication Date: 9 May 2012

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The influence of a gate voltage on domain wall (DW) propagation is investigated in ultrathin Pt/Co/gadolinium oxide (GdOx) films with perpendicular magnetic anisotropy. The DW propagation field can be enhanced or retarded by an electric field at the Co/GdOx interface and scales linearly with gate voltage up to moderate bias levels. Higher gate voltage levels, corresponding to electric fields >0.2 V/nm, produce a large irreversible change to the magnetic anisotropy that can enable nonvolatile switching of the coercivity.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.30.Gw Magnetic anisotropy
75.60.Ch Domain walls and domain structure
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films

Ferromagnetic properties of single walled carbon nanotubes doped with manganese oxide using an electrochemical method

Chang Soo Park, Xiao Zhan Jin, Ki Nam Yun, Young Ran Park, Yoon Shon, Nam-Ki Min, and Cheol Jin Lee

Appl. Phys. Lett. 100, 192409 (2012); http://dx.doi.org/10.1063/1.4714504 (4 pages) | Cited 2 times

Online Publication Date: 9 May 2012

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We report the ferromagnetic doping of single walled carbon nanotubes (SWCNTs) using an electrochemical method. Ferromagnetism was well defined at the low temperature region and the Curie temperature was above 350 K. The coercive field increases monotonically with the increasing manganese concentration. Improved ferromagnetism with the increasing of manganese concentration and the control of hysteresis has been observed, and the electrical transport measurement of SWCNTs shows the normal semiconductor properties. These investigations indicate the great potential of SWCNTs in applications such as spin electronics.
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75.75.-c Magnetic properties of nanostructures
75.78.-n Magnetization dynamics
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.up Other materials

Surface acoustic wave in yttrium iron garnet as tunable magnonic crystals for sensors and signal processing applications

R. G. Kryshtal and A. V. Medved

Appl. Phys. Lett. 100, 192410 (2012); http://dx.doi.org/10.1063/1.4714507 (4 pages) | Cited 1 time

Online Publication Date: 9 May 2012

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Experimental results on investigation of magnonic crystals arising at surface acoustic wave (SAW) propagation in yttrium iron garnet as an artificial structure for surface magnetostatic waves propagation are presented. Tuning of magnonic gap frequency and gap depth were obtained by changing frequency and intensity of SAW that was explained in the frame of inelastic scattering of magnetostatic waves by SAW. Such tuning was shown can compensate drift of parameters due to possible change of temperature when using magnonic crystals as very sensitive magnetic field sensors. Suggested magnonic crystals are promising also for signal processing in GHz range.
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68.35.Iv Acoustical properties
75.30.Ds Spin waves
75.50.Gg Ferrimagnetics

Spatial control of magnetic anisotropy for current induced domain wall injection in perpendicularly magnetized CoFeB|MgO nanostructures

Masamitsu Hayashi, Michihiko Yamanouchi, Shunsuke Fukami, Jaivardhan Sinha, Seiji Mitani, and Hideo Ohno

Appl. Phys. Lett. 100, 192411 (2012); http://dx.doi.org/10.1063/1.4711016 (4 pages) | Cited 1 time

Online Publication Date: 9 May 2012

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Magnetic anisotropy of perpendicularly magnetized CoFeB|MgO films is spatially tailored using depth controlled Ar ion etching with patterned etching masks. Nanowires with patterned etching have significantly reduced coercivity compared to those without the etching. We show that the sign of the anisotropy can be locally changed by partially etching the MgO layer, and as a consequence, 90° domain walls can be created at the boundary of etched/non-etched region. Direct current application to the nanowire can result in moving such 90° domain walls, which can prove as an efficient mean to inject domain walls into perpendicularly magnetized nanowires.
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75.30.Gw Magnetic anisotropy
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ch Domain walls and domain structure
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)
81.65.Cf Surface cleaning, etching, patterning

Fast switching of a ground state of a reconfigurable array of magnetic nano-dots

Roman Verba, Gennadiy Melkov, Vasil Tiberkevich, and Andrei Slavin

Appl. Phys. Lett. 100, 192412 (2012); http://dx.doi.org/10.1063/1.4714772 (3 pages) | Cited 1 time

Online Publication Date: 10 May 2012

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We show numerically that a ground state (ferromagnetic or chessboard antiferromagnetic) and microwave absorption frequency of a dipolarly coupled two-dimensional array of axially magnetized magnetic nano-dots can be switched by application of bias magnetic field pulses (duration 30–70 ns). Switching to the ferromagnetic state can be achieved by applying a rectangular field pulse along the dot axis while switching to the antiferromagnetic state requires the field pulse oriented in the dot plane and having a sufficiently long trailing edge (tail). Our results prove that arrays of magnetic nano-dots can be used as materials having rapidly reconfigurable magnetic and microwave properties.
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75.75.-c Magnetic properties of nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
78.70.Gq Microwave and radio-frequency interactions
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