119Sn Mo spacing diaeresis ssbauer and magnetization studies of the Heusler alloy Ni2Mn1.48Sn0.52

The results of experimental investigations of the crystal structure, magnetization and Mo center dot ssbauer spectroscopy of the Heusler alloy Ni2Mn1.48Sn0.52 are reported. The alloy undergoes the martensitic transition from the L21-type cubic structure into 4O-type orthorhombic structure with a thermal hysteresis of -23 K. The martensitic transition temperature TM is 309 K. The Curie temperature in the austenitic phase TCA of Ni2Mn1.48Sn0.52 is found to be 316 K. The Mo center dot ssbauer spectra from the high temperature paramagnetic state at 330 K and the martensitic state at 283 K were both singlets, showing a typical paramagnetic feature in the narrow temperature range just below TM. With further decrease of temperature, the ferromagnetic ordered state also appears in the martensitic phase. The Curie temperature in the martensitic phase TCM is found to be 256 K. Furthermore, the exchange bias effect is observed in the temperature range 1.8 K <= T <= TB (-130 K), where TB is an exchange bias blocking temperature. The values of a hyperfine magnetic field at Sn nuclei of Ni2Mn1.48Sn0.52 fall significantly below the molecular magnetic field approximation for S = 1. On the basis of the experimental results, the electronic and magnetic properties of Ni2Mn1.48Sn0.52 are discussed.