Signatures of unconventional magnetism in the layered metallic ferromagnet LaCrSb$_3$ from ferromagnetic resonance spectroscopy

Abstract

LaCrSb$_{3}$ is a metallic ferromagnet with a layered crystal structure demonstrating intriguing electronic and magnetic properties, such as large anomalous Hall effect, strong canting of the spin lattice, and a peculiar spin-reorientation transition. Here, we report the results of the temperature-dependent x-ray diffraction, static magnetization, and in particular electron spin resonance (ESR) and ferromagnetic resonance (FMR) experiments carried out over a wide range of frequencies, magnetic fields, and temperatures. Though x-ray data reveals no structural transition down to 15 K, a strong magneto-elastic coupling is detected across the ferromagnetic transition at $T_{\rm C} \simeq 126$ K. ESR results indicate a presence of the quasi-static short-range correlations extending far above $T_{\rm C}$, which is a typical fingerprint of the low-dimensional magnetism. The frequency-field diagram of the FMR modes mapped below $T_{\rm C}$ strongly suggests presence of two magnetic sublattices in LaCrSb$_{3}$. A quantitative understanding of the FMR excitations was achieved within a phenomenological model of interacting orthogonal ferro- and antiferromagnetic sublattices which was earlier proposed to explain unusually strong spin canting observed by neutron diffraction [E.~Granado et al., Phys. Rev. Lett. 89, 107204 (2002)]. The FMR results corroborate this scenario and call for the development of the underlying microscopic model of unconventional magnetism in LaCrSb$_{3}$.