Field-Induced Spin-Structural Transition and Giant Magnetostriction in Ising Chain α-CoV₂O₆

Abstract

We have investigated the temperature and magnetic field dependence of magnetization, specific heat (C p ), and relative sample length change (∆L/L 0 ) for understanding the fieldinduced spin-structural change in quasi-one-dimensional spin chain α-CoV 2 O 6 which undergoes antiferromagnetic (AFM) transition below T N =15 K. Analysis of C p (T ) shows that an effective S=1/2 Ising state is realized below 20 K, though the magnetic fluctuations persist well above T N . C p and the coefficient of linear thermal expansion (α) exhibit strong H dependence in the AFM state. We also observe a huge positive magnetostriction [∆L(H)/L 0 ] below 20 K which does not show any tendency of saturation up to 9 T. With increasing field, a sharp and symmetric peak emerges below T N in both C p (T ) and α(T ) due to field-induced first order ferrimagnetic/ferromagnetic-paramagnetic transitions. The large value of magnetostriction below T N suggests strong spin-lattice coupling in α-CoV 2 O 6 .

Magnetic Structure of Ground and Field Induced Ordered States of Low-Dimensional γ-CoV2O6

“…While each plateau corresponds in single crystals to only one magnetic configuration (AF, Fi, or F), due to the random distribution of the anisotropy axes, the magnetic state will be characterized by a mixture of the different magnetic configurations: AF + Fi for a field between 0.4 and 0.6 T and AF + Fi + F above 0.6 T. This mixture of magnetic configurations is therefore expected during the PND measurements recorded under magnetic field. Note that such behavior was already reported for α-CoV 2 O 6 18 and other polycrystalline low-dimensional compounds. 28 The atomic parameters refined on PND measurement at 300 K ( Figure 3a However, some small peaks could not be indexed in absence of a second propagation vector k AF2 = (1/4, 1/2, 0) necessary to fully describe the magnetic structure.…”

Magnetic and magnetocaloric properties of quasi-one-dimensional Ising spin chain CoV2O6

“…From those plots, one can see that the peak at T F I is much sharper than the peak at T N . It is worth mentioning that α-CoV 2 O 6 exhibits huge magnetostriction effect below T N and, similar to heat capacity, the coefficient of thermal expansion exhibits a sharp peak at T F I for an applied field of 2 T. 17 This suggests that magneto-elastic coupling in α-CoV 2 O 6 is quite strong. Usually, the delta-like sharp and symmetric peak in heat capacity indicates first order nature of phase transition.…”

Metastable and localized Ising magnetism in α−CoV2O6 magnetization plateaus

“…Considering the local octahedral field and spin-orbit coupling, the ground state of Co 2+ can be projected onto a j eff = 1 2 [46,47] with the 3 2 spin-orbit levels well separated in energy [45]. α-CoV 2 O 6 differs from rocksalt CoO where a large exchange constant induces strong mixing between the j eff spin-orbit levels [48][49][50].…”