SPIN

Temperature dependence of the tunnel magnetoresistance (TMR) was calculated in range of the quantum-ballistic model in the magnetic tunnel junction (MTJ) with embedded nanoparticles (NPs). The electron tunnel transport through NP was simulated in range of double barrier approach, which was integrated into the model of the magnetic point-like contact. The resonant TMR conditions and temperature impact were explored in detail. Moreover, the possible reasons of the temperature induced resonant conditions were discussed in the range of the lead–tunneling cell (TC)–lead model near Kondo temperature. We also found that redistribution of the voltage drop becomes crucial in this model. Furthermore, the direct tunneling plays the dominant role and cannot be omitted in the quantum systems with the total tunneling thickness up to 5–6nm. Hence, Coulomb blockade model cannot explain Kondo-induced TMR anomalies in nanometer-sized tunnel junctions.

The spin–orbit coupling spin torque consists of the field-like [S. G. Tan et al., arXiv:0705.3502 (2007).] and the damping-like terms [H. Kurebayashi et al., Nat. Nanotechnol. 9, 211 (2014).] that have been widely studied for applications in magnetic memory. We focus, in this paper, not on the spin–orbit effect producing the above spin torques, but on its magnifying the damping constant of all field-like spin torques. As first-order precession leads to second-order damping, the Rashba constant is naturally co-opted, producing a magnified field-like damping effect. The Landau–Liftshitz–Gilbert equations are written separately for the local magnetization and the itinerant spin, allowing the progression of magnetization to be self-consistently locked to the spin.

In this paper, we performed spin simulations at atomistic level to study the temperature dependent properties of perpendicularly magnetized TbFe thin films. The crystallographically amorphous feature of TbFe ferrimagnetic alloys is modeled by using a lattice system with disordered site occupation of rare earth (RE) and transition metal (TM) spins. The simulated Curie temperature ($T_{\text{C}}$) is consistent well with the mean-field approximation theory. With the increase of Tb concentration, the $T_{\text{C}}$ decreases almost linearly, whereas the magnetization compensation temperature ($T_{\text{M}}$) increases gradually until the $T_{\text{C}}$ value is reached. The inter-sublattice exchange coupling strength $J_{\text{TM-RE}}$ between the RE and TM atoms can significantly affect $T_{\text{M}}$, but has less impact on $T_{\text{C}}$. With the increase of Tb concentration, the TbFe sample of high $J_{\text{TM-RE}}$ exhibits a much faster increase in $T_{\text{M}}$ than the sample with low $J_{\text{TM-RE}}$. Moreover, we have tested the simulation code to model the laser pulse induced ultrafast nonequilibrium spin dynamics. As an example, the femto-second pulse laser induced demagnetization and recovery process is clearly reproduced. These features are in a good agreement with the experiments, indicating that the simulation model can capture the basic physics in describing the high temperature dependent magnetic property as well as the ultrafast spin dynamics.

The finiteness of the eikonal approximation to the superstring amplitude is related to unitarity bounds. The Froissart–Gribov bound is used to establish that only the soft pomeron can contribute at lower energies to the parton distribution. A model of the strongly coupled pomeron, consistent with the intercept of the Regge trajectory, is described.

Biomanipulation based on micro/nano structures is an attractive approach for biotechnology. To manipulate biological systems by magnetic forces, the magnetic labeling technology utilized magnetic nanoparticles (MNPs) as a common rule. Ferrofluid, well-dispersed MNPs, can be used for magnetic modification of the surface or as molds to form organized microstructures. For magnetic-based micro/nano structures, different methods to modulate magnetic field at the microscale have been developed. Specifically, this review focused on a new strategy which uses the concept of micromagnetism of patterned magnetic thin film with specific domain walls configurations to generate stable magnetic poles for cell patterning.

Here, we report an investigation of magnetic domain wall (DW) evolution and propagation in Y-shaped permalloy (Py) nanowire (NW) devices. The devices are fabricated using standard electron-beam lithography technique. Each device consists of three connected NWs that form a Y-junction structure with one branch connecting either symmetrically or asymmetrically to a circular disk for DW nucleation. The DW dynamics in the devices are studied by in situ magnetic force microscopy (MFM) by pinning the DWs to triangular notches at each branch of the two devices. We observe that the DW injection field values differ depending on whether they are connected to the circular disks symmetrically or asymmetrically. However, after they pass the Y-junctions, a selection is made by the DWs to propagate easily either through both or through only one particular outgoing branch of the devices. The experimental observations are analyzed by micromagnetic simulation. It can be inferred from the results that the influence of detailed geometrical shape of the devices leads to significantly different interactions among the innate topological defects and the notches with the injected DWs.