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

Anisotropic long-range spin transport in canted antiferromagnetic orthoferrite YFeO3

In antiferromagnets, the efficient transport of spin-waves has until now only been observed in the insulating antiferromagnet hematite, where circularly (or a superposition of pairs of linearly) polarized spin-waves diffuse over long distances. Here, we report long-distance spin-transport in the antiferromagnetic orthoferrite YFeO₃, where a different transport mechanism is enabled by the combined presence of the Dzyaloshinskii-Moriya interaction and externally applied fields. The magnon decay length is shown to exceed hundreds of nanometers, in line with resonance measurements that highlight the low magnetic damping. We observe a strong anisotropy in the magnon decay lengths that we can attribute to the role of the magnon group velocity in the transport of spin-waves in antiferromagnets. This unique mode of transport identified in YFeO₃ opens up the possibility of a large and technologically relevant class of materials, i.e., canted antiferromagnets, for long-distance spin transport.

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.

Orbitally dominated Rashba-Edelstein effect in noncentrosymmetric antiferromagnets

Efficient manipulation of magnetic order with electric current pulses is desirable for achieving fast spintronic devices. The Rashba-Edelstein effect, wherein spin polarization is electrically induced in noncentrosymmetric systems, provides a mean to achieve staggered spin-orbit torques. Initially predicted for spin, its orbital counterpart has been disregarded up to now. Here we report a generalized Rashba-Edelstein effect, which generates not only spin polarization but also orbital polarization, which we find to be far from being negligible. We show that the orbital Rashba-Edelstein effect does not require spin-orbit coupling to exist. We present first-principles calculations of the frequency-dependent spin and orbital Rashba-Edelstein tensors for the noncentrosymmetric antiferromagnets CuMnAs and Mn[Formula: see text]Au. We show that the electrically induced local magnetization can exhibit Rashba-like or Dresselhaus-like symmetries, depending on the magnetic configuration. We compute sizable induced magnetizations at optical frequencies, which suggest that electric-field driven switching could be achieved at much higher frequencies.

How to manipulate magnetic states of antiferromagnets

Antiferromagnetic materials, which have drawn considerable attention recently, have fascinating features: they are robust against perturbation, produce no stray fields, and exhibit ultrafast dynamics. Discerning how to efficiently manipulate the magnetic state of an antiferromagnet is key to the development of antiferromagnetic spintronics. In this review, we introduce four main methods (magnetic, strain, electrical, and optical) to mediate the magnetic states and elaborate on intrinsic origins of different antiferromagnetic materials. Magnetic control includes a strong magnetic field, exchange bias, and field cooling, which are traditional and basic. Strain control involves the magnetic anisotropy effect or metamagnetic transition. Electrical control can be divided into two parts, electric field and electric current, both of which are convenient for practical applications. Optical control includes thermal and electronic excitation, an inertia-driven mechanism, and terahertz laser control, with the potential for ultrafast antiferromagnetic manipulation. This review sheds light on effective usage of antiferromagnets and provides a new perspective on antiferromagnetic spintronics.