Magneto-transport and domain wall scattering in epitaxy L1 MnAl thin film

Luo, Linqiang; Anuniwat, Nattawut; Dao, Nam; Cui, Yishen; Wolf, Stuart A.; Lu, Jiwei

doi:10.1063/1.4943769

Cited by 12 publications

(10 citation statements)

References 38 publications

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“…The deposition details can be found elsewhere. [15] The complete structure of the multilayer is SiO 2 (substrate)/20nm Ru/2.2nm Co 90 Fe 10 (reference layer)/5nm Cu/6.5nm Ni 80 Fe 20 (free layer)/5nm Ru/Ti 5nm/Au 25nm. A magnetoresistance (MR) of ~1.2% was measured in the pseudo spin-valve continuous film using current-in-plane method before the patterning process [ Fig.…”

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Spin-torque oscillation in large size nano-magnet with perpendicular magnetic fields

Luo

Kabir

Dao

et al. 2017

Journal of Magnetism and Magnetic Materials

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DC current induced magnetization reversal and magnetization oscillation was observed in 500 nm large size Co 90 Fe 10 /Cu/Ni 80 Fe 20 pillars. A perpendicular external field enhanced the coercive field separation between the reference layer (Co 90 Fe 10 ) and free layer (Ni 80 Fe 20 ) in the pseudo spin valve, allowing a large window of external magnetic field for exploring the free-layer reversal. The magnetization precession was manifested in terms of the multiple peaks on the differential resistance curves. Depending on the bias current and applied field, the regions of magnetic switching and magnetization precession on a dynamical stability diagram has been discussed in details. Micromagnetic simulations are shown to be in good agreement with experimental results and provide insight for synchronization of inhomogenieties in large sized device. The ability to manipulate spin-dynamics on large size devices could prove useful for increasing the output power of the spin-transfer nano-oscillators (STNOs).Spin-polarized currents can be harnessed to manipulate magnetization and excite oscillation via the spin transfer torque (STT) effect, and are utilized in the application of MRAM [1,2] and spin-transfer nano-oscillators (STNOs) [3,4] . STNOs have the advantages that their frequencies are highly tunable by current and magnetic field over a range from 2 a few GHz to 40 GHz. [3,5] Furthermore, the nanometer sized devices are among the smallest microwave oscillators yet developed [6] and their compatibility with standard silicon processing opens the possibility for on-chip applications. [7,8] However, the bottlenecks for the widespread application of STNOs lies in the enhancement of the output power above the current limit of ~ 0.5µW. [9] It has been suggested that two nano-contact STNOs in close proximity could mutually phase-lock and increase the output power; however phase-locking of more than two STNOs remains technologically challenge. [10][11][12][13][14] Instead of putting an array of STNOs nano-magnets together, we propose to make use of larger sized magnets in the hope that synchronization of multiple domains could lead to higher output power, and firstly we demonstrated that spin-transfer torque can be used to efficiently induce magnetization switching and oscillation in 500 nm large size devices. For large size device, our simulation results have shown that the non-uniform oscillations tend to synchronize with each other and generate coherent oscillation. In addition, large sized nano-magnets can be fabricated more cost-effectively through photolithography rather than using electron beam lithography. 3The magnetic multilayer was synthesized by sputtering in a Biased Target Ion Beam Deposition system (BTIBD). The deposition details can be found elsewhere. [15] The complete structure of the multilayer is SiO 2 (substrate)/20nm Ru/2.2nm Co 90 Fe 10 (reference layer)/5nm Cu/6.5nm Ni 80 Fe 20 (free layer)/5nm Ru/Ti 5nm/Au 25nm. A magnetoresistance (MR) of ~1.2% was measured in the pseudo spin-valve continuous f...

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confidence: 99%

Spin-torque oscillation in large size nano-magnet with perpendicular magnetic fields

Luo

Kabir

Dao

et al. 2017

Journal of Magnetism and Magnetic Materials

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“…Both intrinsic MR near T C and low‐field (LF) MR, occuring due to the existance of interfaces and grain boundaries (GBs), are observed in diversified manganite‐based composite materials . Furthermore, the sign of MR has been found to be reversed in different systems such as La 0.7 Ca 0.3 MnO 3 /SrTiO 3 ultrathin films, La 0.7− x Pr x Ca 0.3 MnO 3 thin films, and magnetic tunnel junctions . Different physical phenomena such as spin flipping of tunneling electrons, surface anisotropy, and pinning of conduction electron spins at defect sites have been found to be responsible for such reversal of MR in the aforementioned systems.…”

Section: Introductionmentioning

confidence: 99%

“…Different physical phenomena such as spin flipping of tunneling electrons, surface anisotropy, and pinning of conduction electron spins at defect sites have been found to be responsible for such reversal of MR in the aforementioned systems. Moreover, several analytical models have been proposed in this direction . For instance, in a model proposed by Sapkota et al, the combined effect of quantum correction to carrier conductivity and bound magnetic polarons has been considered to explain MR sign reversal in Mn‐doped ZnO nanowires.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Temperature‐Dependent Sign Reversal of Magnetoresistance in 99.95% La_0.7Sr_0.3MnO₃ − 0.05% Paraffin Wax Nanocomposite: The Role of Pinning Center at Intergrain Defect Site

Deb

Dey

2019

Physica Status Solidi (b)

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A reasonable modification of an established phenomenological model is developed to investigate the recent report on sign reversal of magnetoresistance (MR) in 99.95% La0.7Sr0.3MnO3(LSMO)−0.05% paraffin wax hybrid nanocomposite system. At zero external magnetic field (H), all the grain boundary (GB) domain walls (DWs) are assumed to remain pinned at the pinning well. Due to depinning of spin‐polarized DWs with H, a negative MR response is observed between 15 K and 300 K. The GB DWs, which are expected to be pinned with strong pinning strength at and below 10 K, have undergone spin‐flip tunneling, thereby increasing the resistance of the composite with H, i.e., positive MR. The strong pinning phenomenon associated with positive MR is analytically modeled using a skewed Gaussian distribution of pinning strength at and below 10 K.

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“…MnAl alloy have L10ordered structure in the compositional range of about 50−60 at. % Mn [6,7], and exhibits a large Ku (> 1 × 10 7 erg/cm 3 ), low α (~0.006), and relatively small MS (< 600 emu/cm 3 ), which are extremely desirable for an STT application [8][9][10][11][12]. In addition, a tunneling magnetoresistance (TMR) effect with a TMR ratio of 2% at room temperature (RT) was experimentally demonstrated in MTJs with an MnAl electrode [13].…”

Section: Introductionmentioning

confidence: 99%

“…In this regard, it is also necessary to choose a suitable underlayer, such as one with a small in-plane lattice mismatch (∆f), good wettability, and less interfacial reaction, to realize high quality L10-MnAl films. Moreover, although there have been many studies regarding the fabrication of L10-MnAl films on several underlayers, for example, GaAs, Cr, TiN, and MgO [8][9][10][11][12], the growth of L10-MnAl films on an underlayer with ∆f < 1% has yet to be attempted.…”

Section: Introductionmentioning

confidence: 99%

Structural characterization and magnetic properties of L10-MnAl films grown on different underlayers by molecular beam epitaxy

Takata

Gushi

Anzai

et al. 2018

Journal of Crystal Growth

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We grow MnAl films on different underlayers by molecular beam epitaxy (MBE), and investigate their structural and magnetic properties. L10-ordered MnAl films were successfully grown both on an MgO(001) single-crystalline substrate and on an Mn4N(001) buffer layer formed on MgO(001) and SrTiO3(001) substrates. For the MgO substrate, post rapid thermal annealing (RTA) drastically improved the crystalline quality and the degree of L10-ordering, whereas no improvement in the crystallinity was achieved by altering the substrate temperature (TS) during MBE growth. However, high-quality L10-MnAl films were formed on the Mn4N buffer layer by simply varying TS. Structural analysis using X-ray diffraction showed MnAl on an MgO substrate had a cubic structure whereas MnAl on the Mn4N buffer had a tetragonal structure. This difference in crystal structure affected the magnetic properties of the MnAl films. The uniaxial magnetic anisotropy constant (Ku) was drastically improved by inserting an Mn4N buffer layer. We achieved a perpendicular magnetic anisotropy of Ku = 5.0 ± 0.7 Merg/cm 3 for MnAl/Mn4N film on MgO and 6.0 ± 0.2 Merg/cm 3 on STO. These results suggest that Mn4N has potential as an underlayer for L10-MnAl.

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Magneto-transport and domain wall scattering in epitaxy L1 MnAl thin film

Cited by 12 publications

References 38 publications

Spin-torque oscillation in large size nano-magnet with perpendicular magnetic fields

Spin-torque oscillation in large size nano-magnet with perpendicular magnetic fields

Modeling of Temperature‐Dependent Sign Reversal of Magnetoresistance in 99.95% La_0.7Sr_0.3MnO₃ − 0.05% Paraffin Wax Nanocomposite: The Role of Pinning Center at Intergrain Defect Site

Structural characterization and magnetic properties of L10-MnAl films grown on different underlayers by molecular beam epitaxy

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Magneto-transport and domain wall scattering in epitaxy L1 MnAl thin film

Cited by 12 publications

References 38 publications

Spin-torque oscillation in large size nano-magnet with perpendicular magnetic fields

Spin-torque oscillation in large size nano-magnet with perpendicular magnetic fields

Modeling of Temperature‐Dependent Sign Reversal of Magnetoresistance in 99.95% La0.7Sr0.3MnO3 − 0.05% Paraffin Wax Nanocomposite: The Role of Pinning Center at Intergrain Defect Site

Structural characterization and magnetic properties of L10-MnAl films grown on different underlayers by molecular beam epitaxy

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Modeling of Temperature‐Dependent Sign Reversal of Magnetoresistance in 99.95% La_0.7Sr_0.3MnO₃ − 0.05% Paraffin Wax Nanocomposite: The Role of Pinning Center at Intergrain Defect Site