Ultrafast spin dynamics and switching via spin transfer torque in antiferromagnets with weak ferromagnetism

Anomalous magnetic properties of RCrTiO5 (R = Dy and Ho) compounds

We have investigated the nature of magnetic ground state of RCrTiO₅ (R  =  Dy and Ho) through dc magnetization and heat capacity measurements. Due to the strong competition between the Cr³⁺ and R ³⁺ sublattice moments, several intriguing phenomena have been observed when the magnetic state is probed at low field. In both the systems, the Cr³⁺ sublattice undergoes a long-range antiferromagnetic ordering below  ∼139 K with a weak ferromagnetic (FM) moment perpendicular to c axis as evident from the hysteresis in M(H) curve. At low fields ([Formula: see text]150 Oe), the zero-field-cooled magnetization shows that the FM component of Cr³⁺ spin and R ³⁺ moments align in the opposite direction with respect to each other and the net moment aligns in the opposite direction to the applied field in the temperature range 136-16 K for DyCrTiO₅ and below 128 K for HoCrTiO₅. For both the samples, the strong coupling between the two magnetic sublattices is manifested in the temperature dependence of coercive field. Another interesting phenomenon, the spin reorientation transition, has been observed below [Formula: see text] K, where the easy axis of FM moment of Cr³⁺ starts to rotate from one crystallographic axis toward another in DyCrTiO₅ but no such transition has been observed in HoCrTiO₅. The other members of RCrTiO₅ series do not show such kinds of interesting magnetic properties.

Field-driven dynamics and time-resolved measurement of Dzyaloshinskii-Moriya torque in canted antiferromagnet YFeO3

Electrical spin switching in an antiferromagnet is one of the key issues for both academic interest and industrial demand in new-type spin devices because an antiferromagnetic system has a negligible stray field due to an alternating sign between sub-lattices, in contrast to a ferromagnetic system. Naturally, questions arise regarding how fast and, simultaneously, how robustly the magnetization can be switched by external stimuli, e.g., magnetic field and spin current. First, the exploitation of ultrafast precessional motion of magnetization in antiferromagnetic oxide has been studied intensively. Regarding robustness, the so-called inertia-driven switching scenario has been generally accepted as the switching mechanism in antiferromagnet system. However, in order to understand the switching dynamics in a canted antiferromagnet, excited by magnetic field, accurate equation of motion and corresponding interpretation are necessary. Here, we re-investigate the inertia-driven switching process, triggered by the strict phase matching between effective driving field, dh/dt, and antiferromagnetic order parameters, l. Such theoretical approaches make it possible to observe the static parameters of an antiferromagnet, hosting Dzyaloshinskii–Moriya (DM) interaction. Indeed, we estimate successfully static parameters, such as DM, exchange, and anisotropy energies, from dynamical behaviour in YFeO₃, studied using terahertz time-domain spectroscopy.