Magnetodielectric coupling in frustrated spin systems: the spinels MCr₂O₄(M = Mn, Co and Ni)

Abstract

We have studied the magnetodieletric coupling of polycrystalline samples of the spinels MCr2O4 (M = Mn, Co and Ni). Dielectric anomalies are clearly observed at the onset of the magnetic spiral structure (Ts) and at the ‘lock-in’ transition (Tf) in MnCr2O4 and CoCr2O4, and also at the onset of the canted structure (Ts) in NiCr2O4. The strength of the magnetodielectric coupling in this system can be explained by spin–orbit coupling. Moreover, the dielectric response in an applied magnetic field scales with the square of the magnetization for all three samples. Thus, the magnetodielectric coupling in this state appears to originate from the P2M2 term in the free energy.

Temperature evolution of the effective magnetic anisotropy in the MnCr2O4spinel

“…Also, when the applied magnetic field is enhanced, both low-temperature anomalies become less defined, as it was previously reported by Mufti et al [19,20]. [19,20,22]. Noticeable, a linear increase of the high field magnetization is clearly observed for temperatures below 30 K. This lineal contribution signals a noncollinear spins arrangement of the MnCr 2 O 4 ferrimagnet.As is stated in references [23,24] in non-collinear configuration the applied magnetic field exerts a torque that could change the angles between the canted magnetic moments; as a result the magnetization increases linearly with the magnetic field.…”

“…Recently, Mufti and collaborators [19,20] have reported that the dielectric and magnetic properties are coupled below T H in powder MnCr 2 O 4 oxide. In addition, recent FMR results on frustrated spinels [21] have related the unusual FMR temperature dependence to phase separation.…”

Magnetic and structural phase transitions in the spinel compoundFe1+xCr2−xMa1, Garlea2, Rondinone3 et al. 2014Phys. Rev. B

“…Moreover, the multiferroic ordering and the dielectric response induced by the magnetic field also have been found in several chromium spinel oxides. 17,[20][21][22]30,31 Substantial experimental and theoretical works have been performed to study the intriguing properties of ACr 2 O 4 . Previously, a largely separate line of research has been devoted to the spin-lattice interaction which is related to the spin frustration and the cooperative Jahn-Teller distortion especially for the compounds involving orbitally active Asite cations.…”

“…Previously, a largely separate line of research has been devoted to the spin-lattice interaction which is related to the spin frustration and the cooperative Jahn-Teller distortion especially for the compounds involving orbitally active Asite cations. 17,[20][21][22]27,[31][32][33][34][35] However, very few materials have been studied from the view point of the coupling between frustration and Jahn-Teller effects by changing the orbital configuration of B-site cation. ions.…”

Effect of Fe Substitution on Structural and Magnetic Properties of NiCr2O4

“…NiCr 2 O 4 has cubic structure with space group F d3m above 310 K and is a promising magneto-dielectric material [3]. Below 310 K, orbital degeneracy on tetrahedral Ni 2 promotes cooperative Jahn-Teller distortion of NiCr 2 O 4 , lowering the average structural symmetry from cubic to tetragonal (I4 1 {amd) [4,5].…”