Magnetolattice coupling, magnetic frustration, and magnetoelectric effect in the Cr-doped FeVO4 multiferroic material and their correlation with structural phase transitions

Abstract

A detailed account of magnetolattice coupling, magnetic frustration, and magnetoelectric effects in ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Cr}}_{x}{\mathrm{VO}}_{4}$ ($x=0\ensuremath{-}1.0$) studied by temperature-dependent synchrotron x ray diffraction (SXRD), temperature- and magnetic-field-dependent dielectric permittivity $\ensuremath{\varepsilon}$, and magnetization measurements are presented in this paper where progressive Cr doping leads to structural transitions from triclinic (T)---monoclinic (M)---orthorhombic (O) symmetries. SXRD data shows an intricate relationship between magnetic, ferroelectric, and lattice degrees of freedom in these systems. ${\mathrm{FeVO}}_{4}$ reaches a magnetically ordered state with two successive antiferromagnetic orderings at ${\mathrm{T}}_{N1}$ (21.85 K) and ${\mathrm{T}}_{N2}$ (15.65 K), having collinear and noncollinear natures, respectively, as evidenced in DC magnetization measurements. Progressive ${\mathrm{Cr}}^{3+}$ incorporation at the ${\mathrm{Fe}}^{3+}$ site in ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Cr}}_{x}{\mathrm{VO}}_{4}$ shifts these transitions to higher temperatures in T phase ($x=0.0$ and 0.10). At $x=0.175$ [in (T $+$ M) phase], these transitions become closer to each other. Beyond this concentration, a single broad antriferromagnetic transition is observed in M $(x=0.20\ensuremath{-}0.30$) and O ($x=0.90\ensuremath{-}1.0$) phases. A nonlinear behavior in isotherm M-H curves below ${\mathrm{T}}_{N2}$ indicates field-induced spin-reorientation transitions at higher magnetic field. In dielectric permittivity $\ensuremath{\varepsilon}$ a sharp peak at ${\mathrm{T}}_{N2}$ in T and near M regions with a minimal suppression because of applied magnetic field is found and no such peak is observed in far M phase. A discontinuity evidenced in electromagnetic susceptibility indicates magnetoelectric effect at the polar to nonpolar transition regions. The structural incongruence in progressive transformation from T to M to O symmetries plays a vital role in controlling the nature of magnetic interactions. Our results indicate a strong correlation between structural transitions, magnetolattice coupling, magnetic frustrations, and magnetoelectric effect in ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Cr}}_{x}{\mathrm{VO}}_{4}$.