4 research outputs found
Magnetic properties of hematite revealed by an ab initio parameterized spin model
Hematite is a canted antiferromagnetic insulator, promising for applications
in spintronics. Here, we present ab initio calculations of the tensorial
exchange interactions of hematite and use them to understand its magnetic
properties by parameterizing a semiclassical Heisenberg spin model. Using
atomistic spin dynamics simulations, we calculate the equilibrium properties
and phase transitions of hematite, most notably the Morin transition. The
computed isotropic and Dzyaloshinskii--Moriya interactions result in a N\'eel
temperature and weak ferromagnetic canting angle that are in good agreement
with experimental measurements. Our simulations show how dipole-dipole
interactions act in a delicate balance with first and higher-order on-site
anisotropies to determine the material's magnetic phase. Comparison with
spin-Hall magnetoresistance measurements on a hematite single-crystal reveals
deviations of the critical behavior at low temperatures. Based on a mean-field
model, we argue that these differences result from the quantum nature of the
fluctuations that drive the phase transitions.Comment: 11 pages, 10 figure
Anisotropic magnetotransport realized in doped hematite
Conventional antiferromagnetic materials have long been recognized for their
time-reversal symmetry, resulting in a zero anomalous Hall coefficient.
However, a paradigm shift occurs when examining easy-axis antiferromagnets and
their spin-flop transition. This transition introduces a magnetic canted
moment, leading to the emergence of a non-zero anomalous Hall signal and the
generation of a non-dissipative transversal current. While high symmetry
systems typically manifest an isotropic Hall effect, our study unveils the
extraordinary behavior exhibited by hematite that becomes conductive due to
small Ti doping. We investigate the magnetotransport in Titanium-doped
hematite, uncovering a highly pronounced and unconventional symmetry. Notably,
this effect displays a remarkable dependence on the crystal orientation of the
material. We establish a compelling correlation between our experimental
observations and the predicted anomalous Hall effect in altermagnets through
symmetry analysis. This study expands our understanding of the Hall effect in
antiferromagnetic materials and sheds light on the intricate interplay between
crystal orientation and unconventional Hall phenomena
Anisotropic long-range spin transport in canted antiferromagnetic orthoferrite YFeO3
International audienceIn antiferromagnets, the efficient propagation 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 propagate 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 nano-meters, 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 propagation 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
Anisotropic long-range spin transport in canted antiferromagnetic orthoferrite YFeO3
International audienceIn antiferromagnets, the efficient propagation 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 propagate 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 nano-meters, 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 propagation 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