NiSi: A New Venue for Antiferromagnetic Spintronics.

Envisaging antiferromagnetic spintronics pivots on two key criteria of high transition temperature and tuning of underlying magnetic order using straightforward application of magnetic field or electric current. Here, it is shown that NiSi metal can provide suitable new platform in this quest. First, the study unveils high-temperature antiferromagnetism in single-crystal NiSi with Néel temperature, TN ⩾ 700 K. Antiferromagnetic order in NiSi is accompanied by non-centrosymmetric magnetic character with small ferromagnetic component in the a-c plane. Second, it is found that NiSi manifests distinct magnetic and electronic hysteresis responses to field applications due to the disparity in two moment directions. While magnetic hysteresis is characterized by one-step switching between ferromagnetic states of uncompensated moment, electronic behavior is ascribed to metamagnetic switching phenomena between non-collinear spin configurations. Importantly, the switching behaviors persist to high temperature. The properties underscore the importance of NiSi in the pursuit of antiferromagnetic spintronics.

Quantum Magnetic Properties in Perovskite with Anderson Localized Artificial Spin-1/2.

Quantum magnetic properties in a geometrically frustrated lattice of spin-1/2 magnet, such as quantum spin liquid or solid and the associated spin fractionalization, are considered key in developing a new phase of matter. The feasibility of observing the quantum magnetic properties, usually found in geometrically frustrated lattice of spin-1/2 magnet, in a perovskite material with controlled disorder is demonstrated. It is found that the controlled chemical disorder, due to the chemical substitution of Ru ions by Co-ions, in a simple perovskite CaRuO3 creates a random prototype configuration of artificial spin-1/2 that forms dimer pairs between the nearest and further away ions. The localization of the Co impurity in the Ru matrix is analyzed using the Anderson localization formulation. The dimers of artificial spin-1/2, due to the localization of Co impurities, exhibit singlet-to-triplet excitation at low temperature without any ordered spin correlation. The localized gapped excitation evolves into a gapless quasi-continuum as dimer pairs break and create freely fluctuating fractionalized spins at high temperature. Together, these properties hint at a new quantum magnetic state with strong resemblance to the resonance valence bond system.

Spin polarization and relaxation in a semiconductor with impurity absorption of circularly polarized light.

The approach based on kinetic equations is used to describe spin polarization of conduction electrons in a semiconductor doped with d or f atoms and subject to circularly polarized radiation. In the stationary state we find analytical expressions for the spin polarization of band electrons, ρ(e), and spin polarization of electrons in the impurity levels, ρ(i). It is shown that the degree of spin polarization of the band electrons is mainly determined by the polarization type of the light. On the basis of numerical results we conclude that ρ(e) and ρ(i) are practically independent of the long-term relaxation processes in the subsystem of magnetic impurities.