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

A detailed account of magnetolattice coupling, magnetic frustration, and magnetoelectric effects in Fe_1-xCrₓVO₄ (x=0-1.0) studied by temperature-dependent synchrotron x ray diffraction (SXRD), temperature- and magnetic-field-dependent dielectric permittivity ε, 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. FeVO₄ reaches a magnetically ordered state with two successive antiferromagnetic orderings at TN1 (21.85 K) and TN2 (15.65 K), having collinear and noncollinear natures, respectively, as evidenced in DC magnetization measurements. Progressive Cr³⁺ incorporation at the Fe³⁺ site in Fe_1-xCrₓVO₄ 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=0.20-0.30) and O (x=0.90-1.0) phases. A nonlinear behavior in isotherm M-H curves below TN2 indicates field-induced spin-reorientation transitions at higher magnetic field. In dielectric permittivity ε a sharp peak at TN2 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 Fe_1-xCrₓVO₄.