Experimental band structure of the nearly half-metallic CuCr2_2Se4_4: An optical and magneto-optical study

Diagonal and off-diagonal optical conductivity spectra have been determined form the measured reflectivity and magneto-optical Kerr effect (MOKE) over a broad range of photon energy in the itinerant ferromagnetic phase of CuCr$_2$Se$_4$ at various temperatures down to T=10 K. Besides the low-energy metallic contribution and the lower-lying charge transfer transition at $E$$\approx$2 eV, a sharp and distinct optical transition was observed in the mid-infrared region around $E$$=$0.5 eV with huge magneto-optical activity. This excitation is attributed to a parity allowed transition through the Se-Cr hybridization-induced gap in the majority spin channel. The large off-diagonal conductivity is explained by the high spin polarization in the vicinity of the Fermi level and the strong spin-orbit interaction for the related charge carriers. The results are discussed in connection with band structure calculations

Piezomagnetic Properties in Altermagnetic MnTe

We examined the piezomagnetic effect in an antiferromagnet composed of MnTe, which is a candidate material for altermagnetism with a high critical temperature. We observed that the magnetization develops with the application of stress and revealed that the piezomagnetic coefficient Q is 1.38$\times10^{-8}$ ${\mu}$B/MPa at 300 K. The poling-field dependence of magnetization indicates that the antiferromagnetic domain can be controlled using the piezomagnetic effect. We demonstrate that the piezomagnetic effect is suitable for detecting and controlling the broken time reversal symmetry in altermagnets