Theoretical modeling of spin quantum cross structure devices with noncollinear ferromagnetic electrodes

Recently, we have proposed a spin quantum cross structure (SQCS) device toward the realization of novel switching devices. The SQCS device consists of two ferromagneticmetalthin films with their edges facing each other at an angle of θ, and sandwiches a few molecules and atoms. In this paper, the calculation of electronic transport has been performed for SQCS devices with the Ni noncollinear magnetic films as both electrodes within the framework of the Anderson Hamiltonian, taking into consideration both polar angle θ, and azimuthal angle ϕ. We have obtained the general noncollinear spin transport formula, and the polar angle dependence of current-voltage characteristics of SQCS devices. The noncollinear spin transport is determined only by the angle θ defined by the inner product of two spins. Also, it is implied that SQCS devices can serve as multivalued memory devices by varying the angle θ

Large magnetocapacitance effect in magnetic tunnel junctions based on Debye-Frohlich model

The frequency dependence of tunneling magnetocapacitance (TMC) in magnetic tunnel junctions (MTJs) is investigated theoretically and experimentally. According to the calculation based on Debye-Frohlich model combined with Julliere formula, the TMC ratio strongly depends on the frequency and it has the maximum peak at a specific frequency. The calculated frequency dependence of TMC is in good agreement with the experimental results obtained in MgO-based MTJs with a tunneling magnetoresistance (TMR) ratio of 108%, which exhibit a large TMC ratio of 155% at room temperature. This calculation also predicts that the TMC ratio can be as large as about 1000% for a spin polarization of 87%, while the TMR ratio is 623% for the same spin polarization. These theoretical and experimental findings provide a deeper understanding on AC spin-dependent transport in the MTJs and will open up wider opportunities for device applications, such as highly sensitive magnetic sensors and impedance-tunable devices

Magnetic properties on the surface of FeAl stripes induced by nanosecond pulsed laser irradiation

We demonstrate the formation of magnetic nanostripes on the surface of Fe52Al48 induced by nanosecond pulsed laser irradiation and investigate their magnetic properties. The magnetic stripe consists of a disordered A2 phase of Fe-Al alloys with Al-oxide along the [110] direction on the (111)-oriented plane. According to the focused magneto-optical Kerr effect measurement, the coercive force of the magnetic stripe obeys the 1/cos theta law, where theta is the field rotation angle estimated from the stripe direction. Also, the jump field can be observed in the magnetic hysteresis loop. These results indicate that the magnetization reversal in the magnetic stripe originates from the domain pinning, showing that the magnetization rotates incoherently