Pramanik, P.; Singha, A.D.; Reehuis, M.; Pittala, S.; Joshi, D.C.; Sarkar, T.; Tovar, M.; Hoser, A.; Hoffmann, J.–U.; Thota, S.: Interplay of lattice-spin-orbital coupling and Jahn–Teller effect in noncollinear spinel TixMn1-x(FeyCo1-y)2O4: a neutron diffraction study. Journal of Physics: Condensed Matter 36 (2024), p. 355601/1-17
10.1088/1361-648X/ad4adc
Abstract:
Local magnetostructural changes and dynamical spin fluctuations in doubly diluted spinel TixMn1‒x(FeyCo1‒y)2O4 has been reported by means of neutron diffraction and magnetization studies. Two distinct sets of compositions (i) x(Ti) = 0.20 and y(Fe) = 0.18; (ii) x(Ti) = 0.40 and y(Fe) = 0.435 have been considered for this study. The first compound of equivalent stoichiometry Ti0.20Mn0.80Fe0.36Co1.64O4 exhibits enhanced tetragonal distortion across the ferrimagnetic transition temperature TC = 258 K in comparison to the end compound MnCo2O4 (TC ∼ 180 K) with a characteristic ratio ct/√2at of 0.99795(8) demonstrating robust lattice-spin-orbital coupling. However, in the second case Ti0.40Mn0.60Fe0.87Co1.13O4 with higher B-site compositions, the presence of Jahn–Teller ions with distinct behavior appears to counterbalance the strong tetragonal distortion thereby ceasing the lattice-spin-orbital coupling. Both the investigated systems show the coexistence of noncollinear antiferromagnetic and ferrimagnetic components in cubic and tetragonal settings. On the other hand, the dynamical ac-susceptibility, χac(T) reveals a cluster spin-glass state with Gabay–Toulouse (GT) like mixed phases behaviour below TC. Such dispersive behaviour appears to be sensitive to the level of octahedral substitution. Further, the field dependence of χac(T) follows the weak anisotropic GT-line behaviour with crossover exponent Φ lies in the range 1.38–1.52 on the H–T plane which is in contrast to the B-site Ti substituted MnCo2O4 spinel that appears to follow irreversible non-mean-field AT-line behaviour (Φ ∼ 3 + δ). Finally, the Arrott plots analysis indicates the presence of a pseudo first-order like transition (T < 20 K) which is in consonance with and zero crossover of the magnetic entropy change within the frozen spin-glass regime.