Transition of the magnetotransport in a Co-TbN system

Unexpected magnetism is investigated by measurements of the magnetic and magneto-transport properties in the two phase-separated thin films of nano-sized TbN clusters embedded in Co matrices. The spin-dependent transport depends strongly on the volume fraction of magnetic TbN clusters, especially on the continuity of the magnetic phase. With decreasing the TbN volume fraction, the giant magnetoresistance (GMR) is reduced and the anisotropic magnetoresistance (AMR) is enhanced. Unlike the GMR observed in Co ₆₈(TbN) ₃₂, the AMR is found in Co ₇₂(TbN) ₂₈. The room-temperature magnetization exhibits a typical ferromagnetic signal mainly due to the Co matrix, while the low-temperature magnetization shows an additional linear magnetic component. This is attributed to the magnetic moment of TbN at temperatures below the ferromagnetic transition temperature T _C = 44 K, and the magnetic moments of TbN are coupled with those of Co. The topological and magnetic images support the magnetic exchange at the boundary between the TbN clusters and the Co matrix.