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This paper presents electron magnetic resonance (EMR) and vibrating sample magnetometry (VSM) study of Heusler alloy Ni 50 Mn 35.5 In 14.5 ribbons prepared by melt spinning. The temperature dependency of the EMR spectra and magnetization was measured during the cooling and heating process in the 180–330 K and 100–450 K temperature ranges, respectively. Both methods reveal thermal hysteresis (structural phase transition) and metamagnetic character of this material. The morphology and composition were investigated by scanning electron microscopy (SEM) with an energy-dispersive spectrometer (EDS).

Martensitic transformation and magnetic properties in directionally solidified Ni45−xCoxCu5Mn39Sn11 (x = 0, 1, 2) alloys were studied. The martensitic transformation temperature decreases with increasing Co concentration, whereas the Curie temperature of austenite increases, what then alters the magnetic state of austenite at the onset of martensitic phase transformation. Concomitantly the effective magnetic moment of austenite increases by 0.7 μ B / f . u . with Co substitution. Under an applied magnetic field of 5 T the peak values of the magnetic entropy changes reach 11.4 J/kgK (x = 1) and 4.5 J/kgK (x = 2). The variations in magnetic entropy are discussed in relation to a stronger ferromagnetic contribution promoted by Co in the martensite phase.

In this paper, the electron magnetic resonance (EMR) of Ni 47 Co 3 Mn 35.5 In 14.5 alloy in ribbon and powder form are investigated. The EMR spectra for ribbons were registered within the temperature ranges 4 K ⩽ T ⩽ 100 K and 140 K ⩽ T ⩽ 380 K and for powdered ribbon within the temperature range 140 K ⩽ T ⩽ 380 K. Additionally, the magnetic properties of ribbon were also studied by using vibrating sample magnetometer (VSM) in the temperature range of 85 K ⩽ T ⩽ 400 K. At high temperature, the EMR signal consist of a single, asymmetric line. The temperature dependence of the inverse integrated intensity exhibits a Curie–Weiss like behaviour and Curie temperature ( T C ) determined from VSM equals 333 K. Below T C for ribbon sample the low field microwave absorption (LFMA) line was observed. The EMR spectra recorded for the powder sample are of a different shape than those for the ribbon sample. The powdering causes an increase of the effective skin depth, and the high-temperature lines lose asymmetric character. The Curie temperature is shifted relative to Curie temperature determined for the ribbon sample, but the structural phase transition is preserved.

The combined effect of ball milling and subsequent heat treatment on microstructure, magnetic, magnetocaloric and exchange bias properties of Ni48Mn39.5Sn10.5Al2 ribbons is reported. The annealing treatment results in the increase of the critical martensitic transformation temperature. The magnetic entropy change ΔSM of the order of 7.9 and −2.3 J kg K−1 for the annealed 50–32 µm powder fraction is determined. This is less than in the as melt spun ribbon but appears at a considerably higher temperature. At the same time EB is decreased due to annealing treatment. This decrease is attributed to the strengthened ferromagnetic exchange coupling due heat induced stress and structural relaxation.

The influence of Al substitution for Sn on magnetocaloric properties and exchange bias behavior in Ni48Mn39.5Sn12.5−xAlx (x=0, 1, 2, 3) melt spun ribbons have been investigated. All the studied ribbons undergo a martensitic and reverse transformation. At low temperature martensite region, below 100 K, the alloys exhibit exchange bias effect, which appears to enhance with the increase of Al concentration. The loop shift difference (ΔHE) of up to 7960 A m−1 is recorded between the ribbon containing no Al and the ribbon with x=3. The presence of exchange bias behavior in these samples is attributed to the coexistence of antiferromagnetic and ferromagnetic exchange interactions. The magnetic entropy change and refrigerant capacity are evaluated for the ribbons studied around both the structural and magnetic transformations under the applied magnetic field induction of 2 T. The maximum entropy change around the magnetic transition and around the structural transition is reported for the Ni48Mn39.5Sn12.5 ribbon, and the entropy values amount to 1.8 and 7.8 J kg−1 K−1, respectively.

Martensitic and magnetic transformations in Ni 48 Mn 39.5 Sn 12.5− x Al x ( x =0, 1, 2, 3) Heusler alloy ribbons were investigated. It is demonstrated that both magnetic and structural transformations occur in all of the studied samples. It is also shown that substitution of Sn with Al causes the martensitic transformation ( MT ) and the reverse martensitic transformation ( RMT ) temperatures to increase to room temperature (Δ T MT =49 K; Δ T RMT =43 K), whereas the Curie temperature of martensite T C M decreases (Δ T =36 K) and the Curie temperature of austenite T C A remains practically insensitive to Al introduction. This then allows to tune T C A and the MT temperature leading to their coincidence at ambient temperature. The austenite phase with the L2 1 type structure has been identified to exist in all the samples regardless of composition. On the other hand the structure of martensite has been shown to be sensitive to composition. It has been determined as the 10 M martensite with ( 3 2 ¯ ) stacking sequence in Al free samples and the 4O martensite with the stacking periodicity ( 3 1 ¯ ) in Al containing samples. In addition, the splitting of the field cooling ( FC ) and the field heating ( FH ) thermo-magnetic curves at low (50 Oe) magnetic field and below the T C M has been attributed to intermartensitic transition. The application of large magnetic field (50 kOe) has shown the existence of two distinct ferromagnetic states with a considerable hysteresis loop. The properties of these materials make them promising for magnetocaloric applications.