Magnetoelectric Effect and Spontaneous Polarization in HoFe$_3$(BO$_3$)$_4$ and Ho$_{0.5}$Nd$_{0.5}$Fe$_3$(BO$_3$)$_4$

TL;DR

This study investigates the magnetic, dielectric, and magnetoelectric properties of HoFe3(BO3)4 and its Nd-doped variant, revealing spontaneous polarization and magnetoelectric effects in the solid solution but not in the pure compound.

Contribution

It demonstrates the emergence of magnetoelectric effects in Ho0.5Nd0.5Fe3(BO3)4, contrasting with the absence of such effects in HoFe3(BO3)4, highlighting the impact of Nd doping.

Findings

HoFe3(BO3)4 shows spontaneous polarization below T_N but no magnetoelectric effect.

Ho0.5Nd0.5Fe3(BO3)4 exhibits both spontaneous polarization and magnetoelectric effect.

Complex polarization behavior results from superposition of internal and external magnetic field effects.

Abstract

The thermodynamic, magnetic, dielectric, and magnetoelectric properties of HoFe$_3$(BO$_3$)$_4$ and Ho$_{0.5}$Nd$_{0.5}$Fe$_3$(BO$_3$)$_4$ are investigated. Both compounds show a second order Ne\'{e}l transition above 30 K and a first order spin reorientation transition below 10 K. HoFe$_3$(BO$_3$)$_4$ develops a spontaneous electrical polarization below the Ne\'{e}l temperature (T$_N$) which is diminished in external magnetic fields. No magnetoelectric effect could be observed in HoFe$_3$(BO$_3$)$_4$. In contrast, the solid solution Ho$_{0.5}$Nd$_{0.5}$Fe$_3$(BO$_3$)$_4$ exhibits both, a spontaneous polarization below T$_N$ and a magnetoelectric effect at higher fields that extends to high temperatures. The superposition of spontaneous polarization, induced by the internal magnetic field in the ordered state, and the magnetoelectric polarizations due to the external field results in a complex behavior of the total polarization measured as a function of temperature and field.