The Phase Relations of the Co-Ni-In Ternary System at 673 K and 873 K and Magnetic Properties of Their Compounds

The phase relationships of the ternary Co-Ni-In system at 673 K and 873 K were investigated by means of powder X-ray diffraction, scanning electron microscopy equipped with energy dispersive spectroscopy, and optical microscopy. Though CoIn(2) does not exist at 873 K, the ternary solid solution Co(1−x)Ni(x)In(2) exists at both 673 K and 873 K with different composition ranges. The Rietveld refinements were carried out to investigate the crystal structure of Co(1−x)Ni(x)In(2) (x = 0.540, and 0.580) and Ni(2−x)Co(x)In(3) (x = 0.200). The magnetization dependence of temperature (MT) curves of Ni(2−x)Co(x)In(3) (x = 0.200) and Co(1−x)Ni(x)In(2) (x = 0.540) are similar to those of the ferromagnetic shape memory alloys Ni-Mn-A (A = Ga, Sn, and In), but do not undergo martensitic transformation. The maximum magnetic entropy changes in Ni(2−x)Co(x)In(3) (x = 0.200) and Co(1−x)Ni(x)In(2) (x = 0.540) under 3T are 1.25 and 1.475 J kg(−1)K(−1), respectively.