Physical Propertie Of The Heusler Alloys NiMnSn-Co

During the last decade, Heusler alloys have been extensively studied since their rich physical properties and potential applications in spintronics devices. Among them, NiMnSn-Co alloy have been growingly investigated since its high magnetic field driving efficiency. In this work, we adopt arc furnace smelting synthesis of a series of Ni50-xCoxMn39Sn11(0≤x≤10) alloys, the crystal structure was checked using X-ray Diffraction (XRD), the magnetic and transport properties were measure by using Vibrating Sample Magnetometer (VSM), Superconductivity Quantum Interference Device (SQUID) and Physical Properties Measurement System(PPMS).As a result, we found that, by varying the Co content, the samples show a rich set of properties:i) The Co content is8.0, implements the drive efficiency of high magnetic fields induce martensite phase transformation; ii) With the increase of Co content, the vales of saturation magnetization gradually increased; iii) From the temperature-dependent magnetization measurements, it was found that with increase of Co content, martensite transformation gradually disappears, which is consistent with the resistance measurement; iv) In addition, according to the results of ac magnetic susceptibility and ZFC/FC measurements, we confirmed that there is exist of superspin glass for samples with Co>8.0, and a clear exchange bias phenomenon is also observed.We demonstrate that the superspin glass martensite and ferromagnetic austenitic parent phase coexist, and we proposed a simple model to explain the origin of exchange bias phenomenon. Finally, we found that as Co content more than8.85, both the super spinglass and exchange bias phenomenon disappear simultaneously.