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Ni50 − x Mn37 + x Sb13 (NMS (x = 4–6)) melt-spun Heusler ribbon was fabricated by employing the arc melting technique. Also, the electrical, structural, and magnetic characteristics of melt-spun alloy ribbons with chemically increased Mn (a decrease in Ni concentration) content are also being investigated. Further, it has been noticed that, the Curie temperatures of the austenitic (T CA) phase and the martensitic phase transition temperature (T M) are both shifted toward higher temperatures, by increasing the amount of Mn under 500 Oe (0.05 T) of applied magnetic fields. The discontinuity of field cooling (FC) and zero field cooling (ZFC) curves reveals the irreversibility of magnetization caused by inhomogeneous magnetic anisotropy lower the exchange bias (EB) (blocking bias) temperature. Furthermore, the disappearance of exchange bias (EB) in ribbon alloys with increasing temperature is supported by the fact that coercivity (H C) gradually increases with temperature and increases at 40 K, and then decreases with temperature. Additionally, a −Δ S Max of −5.21 Jkg−1·K−1 for a ribbon with x = 6 is acquired at 312 K with a 50 kOe (5 T) change in the applied magnetic field. Increases in Mn content result in −Δ S M values in NMS alloy ribbons of −4.3, −4.7, and −5.2 Jkg−1·K−1 and the same trend is observed in negative magneto-resistance ((−MR) (%)) values of −9%, −11%, and −14% for x = 4–6, respectively. Here, the super zone boundary that is close to the Fermi surface is responsible for the change in −MR. [ABSTRACT FROM AUTHOR]

The effect of partial substitution of manganese by silicon in Ni47Mn40−xSixIn13 (x = 1, 2, 3) on the structural (martensitic), magnetic transitions and associated magnetocaloric properties around the martensitic transition of these alloys, was investigated. The alloys exhibited the single austenite structure at the room temperature. The lattice contraction was observed with an increase in Si content, thereby inducing the FM and AFM interactions between manganese atoms, which further influence the magnetic and martensitic transitions. The increase in Si concentration was observed with the decrease in valence electron to atom ratio (e/a ratio) and thus influencing the martensitic transitions. The transition temperatures such as martensitic transition (TM) and the Curie transition (TC) of the austenite phase decrease with increasing Si-content. With the increase in Si content from x = 1 to 3, the TM was found to decrease from 259 to 169 K. A high magnetic entropy change (∆S)M of 12.3, 3.1 and 30.6 J kg−1 K−1 was observed for the x = 1, 2, and 3 alloys at their respective martensitic transitions for a magnetic field of 2 T. [ABSTRACT FROM AUTHOR]

The effect of partial Si substitution for Sn on the structure, magnetism, magnetic entropy change, exchange bias and negative magnetoresistance in Ni48Mn39Sn13−xSix(1 ≤ x ≤ 4) Heusler alloy systems is investigated. A small amount of Si in the Sn position influences the characteristic transition temperatures and the magnetocaloric effect. A maximum positive entropy change of 5.13 J kg−1 K−1 is observed for a field change of 9 T in the x = 1 alloy. An increase in Si content increases the exchange bias field. The exchange bias field and the coercive field strongly depend on the Si content. For the x = 4 alloy, an exchange bias field of 354 Oe is observed. In addition, a negative magnetoresistance is observed in this alloy system, which decreases with Si content. The increase in resistivity at the martensitic transition could be attributed to the formation of superzone boundary gaps that changes the density of states near the Fermi surface. [ABSTRACT FROM AUTHOR]