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Magnetic and magnetocaloric properties of quasi-one-dimensional Ising spin chain CoV$_{2}$O$_{6}$

We have investigated the magnetic and magnetocaloric properties of antiferromagnetic Ising spin chain CoV$_{2}$O$_{6}$ by magnetization and heat capacity measurements. Both monoclinic $α$-CoV$_{2}$O$_{6}$ and triclinic $γ$-CoV$_{2}$O$_{6}$ exhibit field-induced metamagnetic transition from antiferromagnetic to ferromagnetic state via an intermediate ferrimagnetic state with 1/3 magnetization plateau. Due to this field-induced metamagnetic transition, these systems show large conventional as well as inverse magnetocaloric effects. In $α$-CoV$_{2}$O$_{6}$, we observe field-induced complex magnetic phases and multiple magnetization plateaux at low temperature when the field is applied along $c$ axis. Several critical temperatures and fields have been identified from the temperature and field dependence of magnetization, magnetic entropy change and heat capacity to construct the $H$-$T$ phase diagram. As compared to $α$-CoV$_{2}$O$_{6}$, $γ$-CoV$_{2}$O$_{6}$ displays a relatively simple magnetic phase diagram. Due to the large magnetic entropy change and adiabatic temperature change at low or moderate applied magnetic field, $γ$-CoV$_{2}$O$_{6}$ may be considered as a magnetic refrigerant in the low-temperature region.