Inverse melting and intertwined orders in PrCuSb$_2$

Abstract

Much of the rich physics of correlated systems is manifested in the diverse range of intertwined ordered phases and other quantum states that are associated with different electronic and structural degrees of freedom. Here we find that PrCuSb$_2$ exhibits such phenomena, which at ambient pressure exhibits a fragile antiferromagnetic order, where cooling in a small $c$ axis magnetic field leads to an additional transition to a field-induced ferromagnetic state. This corresponds to an 'inverse melting' effect, whereby further cooling the system restores symmetries of the paramagnetic state broken at the antiferromagnetic transition. Moreover, hydrostatic pressure induces an additional first-order transition at low temperatures, which despite being not likely associated with solely magnetic degrees of freedom, is closely entwined with the magnetic order, disappearing once antiferromagnetism is destroyed by pressure or magnetic fields. Consequently, PrCuSb$_2$ presents a distinct scenario for interplay between different orders, underscoring the breadth of such behaviors within one family of correlated materials.