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We have investigated the magnetic properties of highly anisotropic layered ferromagnetic semiconductor CrI3 under hydrostatic pressure with magnetic field along the easy-axis of magnetization. At ambient pressure, CrI3 undergoes a second-order paramagnetic to ferromagnetic phase transition at TC =60.4 K. TC is found to increase sublinearly from 60.4 to 64.9 K as pressure increases from 0 to 1.0 GPa. With the increase in pressure, the transition becomes sharper while magnetization at low-field decreases monotonically due to the decrease in magnetocrystalline anisotropy. The weak low-field anomaly at around 48 K, resulting from the two-step magnetic ordering, also shifts toward higher temperature with increasing pressure. The observed increase in TC and the decrease in magnetization could originate from change in coupling between the layers and Cr-I-Cr bond angle with pressure.

We report the effect of exchange frustration on the magnetocaloric properties of GdCrTiO5 compound. Due to the highly exchange-frustrated nature of magnetic interaction, in GdCrTiO5, the long-range antiferromagnetic ordering occurs at much lower temperature TN =0.9 K and the magnetic cooling power enhances dramatically relative to that observed in several geometrically frustrated systems. Below 5 K, isothermal magnetic entropy change (-∆Sm) is found to be 36 J kg −1 K −1 , for a field change (∆H) of 7 T. Further, -∆Sm does not decrease from its maximum value with decreasing in T down to very low temperatures and is reversible in nature. The adiabatic temperature change, ∆T ad , is 15 K for ∆H=7 T. These magnetocaloric parameters are significantly larger than that reported for several potential magnetic refrigerants, even for small and moderate field changes. The present study not only suggests that GdCrTiO5 could be considered as a potential magnetic refrigerant at cryogenic temperatures but also promotes further studies on the role of exchange frustration on magnetocaloric effect. In contrast, only the role of geometrical frustration on magnetocaloric effect has been previously reported theoretically and experimentally investigated on very few systems. arXiv:1805.02056v1 [cond-mat.mtrl-sci]

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