Origin of metamagnetism in skyrmion host Cu$$_2$$OSeO$$_3$$

Abstract

Skyrmion host chiral Cu\(_2\)OSeO\(_3\) has attracted researchers due to several intriguing properties. Observation of metamagnetism in low-temperature and low-field makes the magnetic properties of Cu\(_2\)OSeO\(_3\) more complex. Here, we present an investigation on metamagnetism in Cu\(_2\)OSeO\(_3\) by analyzing its structural and magnetic properties. Study of magnetic properties reveal spin-flip of one of the Cu\(^{2+}\) ions, embedded in square pyramidal CuO\(_5\) polyhedra, due to the development of strain in low-temperature and low-field regime. The spin-flip is found to be the main reason for field-induced first-order metamagnetic transition. Magnetic phase diagram of Cu\(_2\)OSeO\(_3\) has been constructed with the help of magnetization analyses. It is argued that the metamagnetic hysteretic field region may be low-temperature skyrmion phase with additional spiral and tilted-conical phases. A tricritical point has been observed in the phase diagram at which first-order metamagnetic hysteretic field range ceases to exist.