Abstract
Recently, an attention has been paid to outstanding magnetic properties of martensitic phase of the Co-doped Heusler Ni2MnGa alloys with a paramagnetic gap that can be tuned by composition. We have prepared polycrystalline sample of Co doped Ni2MnGa alloy, Ni43Co7Mn31Ga19, with the very small amount of Er (0.1at.%).
By the EDX analysis, a distinct segregation of Er was discovered in Er-rich phase while the main bulk material of the microcrystals was totally Er-free. Saturated magnetization M(5 K)= 3.27 mu(B)/f.u. and the Curie temperatures T-C(A) = 453 K of austenite phase, were observed by a SQUID magnetometer on annealed sample and the standard magnetocaloric effect at vicinity of T-C(A) was measured by direct method with Delta T = 0.6 K.
Magnetic susceptibility obeys nicely the Curie-Weiss law with paramagnetic moment of mu(eff) = 5.09 mu B/f.u. above T-C(A). However in the pronounced contrast with the Er-free alloys, both, the paramagnetic gap and mainly the martensitic transitions were not observed in the Er conditioned Ni43Co7Mn31Ga19 sample.