Recently published

Hyperfine interactions enable spin-orbit torque on nuclear spin

Hyperfine interactions describe the magnetic interaction between spins of atomic nucleus and electron. The interaction, also referred as hyperfine coupling, consists of Fermi contact and dipolar interactions between dipole magnetic moments of atomic nucleus and electron. We demonstrate that the hyperfine coupling can mediate the application of spin-orbit torques acting on nuclear spins. In quantum computing, nuclear spin is a candidate for qubit. Since qubit has the potential to the miniaturization of memory, the application of nuclear spin by means of nuclear spin orbit torque could lead to further miniaturization of spintronics devices.

Spin-orbit couplings at magnetic interface generate magnetoelectric effect and enable exchange bias

Exchange bias is a unidirectional magnetic anisotropy that often arise from interfacial interaction of a ferromagnetic and antiferromagnetic layers. we show that spin-orbit couplings in magnetic heterostructures, such as La2/3Sr1/3MnO3|LaAlO3|SrTiO3 can induces an exchange bias via an interface magnetoelectric effect. The interface magnetoelectric effect is induced by spin-orbit couplings that arises from the broken symmetry of the system. We demonstrate that the exchange bias can be controlled by electric field.

Twisted spin density generates anisotropic magnetic interactions.

The interactions of spins -most miniature magnets- can be isotropic or anisotropic, the latter resulting in twisted spin orientations. This article finds a simple explanation of the anisotropic interaction named Dzyaloshiskii-Moriya in metals. The model is based on two atomic spins; one of them is heavy, such as a lanthanide. As a result, a spin orientation emerges in the electrons of the metal and is perpendicular to the atomic spins. We name this as Dzyaloshisnkii-Moriya Spin-Density (DM-SD). When additional magnetic atoms are considered, the DM-SD mediates their interaction, similar to the magnetic field of large magnets’ poles, or the isotropic polarization in metals connecting far spins. The figure shows three spins (one of them, Jf, a lanthanide) and the DM-SD (colormap and small arrows) mediating their exchange.

Orbital hybridization enhances interface phenomenon

In chemistry, the mixing of atomic orbitals form orbital hybridization. The orbital hybridization helps to explain molecule shape. In a carbon atom, for example, s and p orbitals form s-p orbital hybridization. In the band theory of solid state, orbital hybridization can also occur. For example, in the Anderson impurity model, an impurity in a sea of conduction electrons is modeled as a localized orbital and an itinerant orbital. The orbital hybridization enables the interaction between the bands. In this article, we study a spin current generation phenomenon at the interface of a magnetic material and a heavy metal. The heavy metal can be described using a generalized Anderson model with s-d orbital hybridization. By comparing the data of various heavy metals, we show that the s-d orbital hybridization enhances the spin current generation.

Book:

A.B. Cahaya, Fungsi khusus dan persamaan diferensial dalam fisika matematika (UI Publishing, Jakarta, 2022).