Analytical Descriptions of Magnetic Properties and Magnetoresistance in n-Type HgCr_2Se_4

We present a detailed investigation of magnetic properties of colossal magnetoresistance material HgCr_2Se_4. While spontaneous magnetization and zero-field magnetic susceptibility are found to follow asymptotic scaling laws for a narrow range of temperatures near the critical point, two methods with connections to the renormalization group theory provide analytical descriptions of the magnetic properties for much wider temperature ranges. Based on this, an analytical formula is obtained for the temperature dependence of the low field magnetoresistance in the paramagnetic phase.