Magneto-resistance of MnFe(As,P)

Summary form only given. The phosphide-arsenide MnFe(As,P) system exhibits not only peculiar structural and magnetic properties but also exhibits a giant magnetocaloric effect. Currently, there exists only little information about the electrical-transport properties for this system. Here, we report on the electrical resistance and magneto-resistance of MnFeP/sub 0.55/As/sub 0.45/. Polycrystalline samples were prepared by solid state reaction. X-ray powder diffraction shows that the compound crystallizes in the hexagonal Fe/sub 2/P structure type. The resistance and the magneto-resistance (MR) were measured as a function of temperature and magnetic field by a standard four-probe technique. The temperature dependence of the electrical resistance normalized at room temperature for the sample measured during cooling in zero field is presented. The resistance is maximal around T/sub cr/=231 K and the extremum in the temperature derivative of the /spl rho/-T curve coincides with the Curie temperature. This has been tentatively attributed to the change in c/a ratio accompanying the transition at T/sub cr/, which in turn affects the electronic structure of the compound. The resistance of the sample is almost temperature independent around room temperature. The increase in resistivity on approaching the magnetic-ordering temperature may be related to the existence of antiferromagnetic fluctuations. This is corroborated by the observation of a positive MR. The temperature dependence of the MR ratio defined as /spl Delta/R/R/sub 0/=R(H,T)-R(0,T)/R(0,T) above the transition temperature is shown. The critical field and the MR both increase with temperature. The MR ratio is up to 70% in 9 T field.