Spin Dynamics and Light-Induced Effects in EuZn$_2$P$_2$

TL;DR

This study investigates the magnetic spin dynamics, optical properties, and light-induced effects in EuZn₂P₂, revealing anisotropic magnetic behavior, formation of magnetic polarons, and a photovoltaic effect, indicating potential for optoelectronic applications.

Contribution

It provides new insights into the spin relaxation mechanisms, magnetic interactions, and light-induced phenomena in EuZn₂P₂, including the discovery of photovoltaic effects in this material.

Findings

EuZn₂P₂ orders antiferromagnetically at 23.5 K.

ESR reveals anisotropic spin relaxation and magnetic polarons.

Photovoltaic effect observed under light illumination.

Abstract

The magnetic spin dynamics and optical properties of EuZn$_2$P$_2$ are studied. Single crystals grown by the Sn-flux method crystallize in the $P\overline{3}m1$ (No.~164) space group and order antiferromagnetically at $T_N=23.5$~K. $^{151}$Eu M\"ossbauer spectroscopy confirms the presence of the Eu$^{2+}$ oxidation state only and the magnetic moment angle relative to the $c$-axis is $\theta=46(3)$\textdegree. Temperature-dependent electron spin resonance (ESR) measurements reveal that spin-spin interactions predominantly govern the spin relaxation mechanisms, as evidenced by the linewidth behavior ($\Delta H$). Positive $g$-shifts ($\Delta g)$ for $H \parallel ab$ indicate the presence of local electron polarization. The ESR data support the formation of anisotropic magnetic polarons, which trap spin carriers and contribute to increased electrical resistance. Angular-dependent ESR spectra at room temperature display anisotropic behavior in both $\Delta g(\phi)$ and $\Delta H(\phi)$, with a dominant three-dimensional component $C_{3D}$, indicative of robust interlayer coupling and antiferromagnetic fluctuations. Under light illumination, a small broadening of $\Delta H$ is observed. Furthermore, a photovoltaic effect is identified in EuZn$_2$P$_2$, with photodetector performance metrics suggesting promising capabilities for future optoelectronic devices.