Effects of Rare-Earth (R = Pr, Gd, Ho, Er) Doping on Magnetostructural Phase Transitions and Magnetocaloric Properties in Ni43-xRxMn46Sn11 Shape Memory Alloys

A series of rare-earth-doped Ni43-xRxMn46Sn11 (x = 0, 1 and R = Pr, Gd, Ho, Er) alloys was fabricated by arc melting, and their structural, magnetic, and magnetocaloric properties were studied through room temperature X-ray diffraction (XRD), differential scanning calorimetry, and magnetization measurements. Analysis of XRD data reveal that the alloys crystallize in the cubic L2(1) austenite phase structure as the major phase with a small trace of martensitic phase (MP). The martensitic transition temperature (T-M) shifts to consecutive higher temperatures with the substitution of Pr, Gd, Ho, and Er. A drastic shift in T-M by similar to 60 K relative to the parent compound (T-M = 195 K) was found for Ni42PrMn46Sn11. Large values of magnetic entropy changes (Delta S-M) of 32 (Pr), 28 (Gd), and 25 J . kg(-1) . K-1 (Ho) were obtained at T-M for Delta H = 50 kOe. A maximum value of the refrigeration capacity of similar to 250 J . kg(-1) was obtained in the vicinity of T-M for Delta H = 50 kOe for the Ho-doped compound. A large exchange bias effect with H-EB similar to 1.1 kOe at 10 K was observed for the Pr-doped compound in its MP.