Magnetoresistance due to Electron-Spin Scattering in Antiferromagnetic Metals at Low Temperatures

Abstract

1401 The magnetoresistance due to electron-spin scattering in antiferromagnetic metals is obtained in the low-temperature region to 6e order of J2 assuming that the s-d interaction J is small, i.e, T N'PT-:PJ. Compared with the results in the simple molecular field approximation, the magnetoresistance shows a large increase at the antiferro-paramagnetic transition point Hc2· § I. Introduction The magnetoresistance of magnetic metals is an interesting phenomena in which transport properties couple with magnetism. In magnetic metals there are several origins of the magnetoresistance. One is the change of relaxation time due to the magnetic· field or the change of the scattering mechanism, and another is the change of the carrier number, i.e., change of the band structure. The effect of the long-range order on tpe energy spectrum of conduction electron is the example of the latter, and the change of spin fluctuation is the example of the former. In a perivous paper 1 l the positive magnetoresistance due : to electron-spin scattering in antiferromagnetic metals was obtained in the molecular field approximation for the spin fluctuation for the case of weak magnetic field such as rwH<-.1, where r is the relaxation time of the conduction electron and WH is the cyclotron frequency. Such approximation becomes insufficient at low temperatures or near the Neel temperature TN' and the effect of the spin collective mode or the· spacial spin correlation must be taken into account; In this paper we employ the RP A for the spin correlation function and calculate the resistivity due to electron-spin scattering in the low-temperature region within the first Born approximation. In § 2 the model and the approximation are explained and the spin Green functions are obtained in the RP A. In § 3 the resistivity due to spin fluctuation is calculated and the dependence on. the magnetic field is examined. The last section is devoted to the summary and discussion. In the Appendix the magnetoresistance which comes from another origin (normal magnetoresis-tance, etc.) is briefly derived within the hydrodynamical approximation of the Kubo formula employed in the present paper.