Electronic and Magnetic Properties of Pt Based Intermetalic LaPtAs and LaPt ₂ As Compounds

We report the synthesis of polycrystalline LaPtAs and LaPt ₂ As via solid state reactions and their temperature dependent magnetic and electrical transport properties. Crystal structures of both samples are suggested to be orthorhombic with a Pmmm space group. Temperature and field dependent magnetization measurements show that the splitting of field cooling and zero field cooling curves (initiation of irreversibility) take place at temperatures just below the Curie temperatures for both samples. This behavior is a characteristic of magnetic nanoparticles. Therefore, we propose that the magnetization arises from nanosized platinum clusters due to partial filling of the available interstitial sites. Temperature (T) dependent resistivity measurements of both alloys show metallic behavior at high temperatures and resistivity curve bends away from classical linear T dependence toward the temperature axis in the intermediate temperature range. This behavior is attributed to phonon induced interband s–d scattering. The main contribution to the resistivity at low temperatures is suggested to arise from the scattering of conduction electrons by spin-waves, in the presence of strong spin–orbit coupling due to Pt atoms. We discuss the role of spin–orbit effect on the electronic structure and the magnetic state of both samples based on various nano-scale structures.