Magnetic and dielectric properties of metamagnetic TbCo 0.5 Mn 0.5 O 3.07 ceramics

The ceramic TbCo 0.5 Mn 0.5 O 3.07 of double-perovskite structure was prepared by solid-state reaction. Its crystal structure and magnetic and dielectric properties were investigated by first-principles calculations and experimental observations. TbCo 0.5 Mn 0.5 O 3.07 possesses a monoclinic structure with P 2 1 / n space group. The c axis is the easy-magnetization axis, and it is largely caused by Co 2+ anisotropy. The predominant valence states are Mn 4+ and Co 2+ , with a small amount of Co 3+ coexisting with Co 2+ . The ordering of Mn 4+ and Co 2+ results in ferromagnetic Mn 4+ –Co 2+ interactions. Partial disorder of the B-site creates antiferromagnetic Co 2+ –O–Co 2+ or Mn 4+ –O–Mn 4+ interactions. The origin of metamagnetism is associated with the coexistence of antiferromagnetic and ferromagnetic phases. The magnetic exchange bias is strongly dependent on magnetic field, which is considered to be related to the metamagnetic behavior. The possibility of spin glass behavior is excluded by AC susceptibility measurements. The two observed dielectric relaxations are caused by electrons hopping between Co 2+ and Mn 4+ and between Co 3+ and Mn 4+ .