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In this work, we have investigated magnetic properties, the magnetocaloric effect, and critical behavior in the Fe79Cr6B2Nd3Zr10 amorphous alloy ribbon prepared by the melt-spinning method. This alloy undergoes a second-order ferromagnetic–paramagnetic (FM–PM) phase transition around its Curie temperature TC ≈ 300 K. A large value of maximum entropy change, |ΔSm|max ≈ 1 J kg−1 K−1, was achieved for a magnetic field change of 12 kOe in a wide range of operative temperature. To clarify the nature of the FM–PM phase transition and magnetic interactions in the alloy, a set of critical parameters (β, γ) has been determined using two different methods. The obtained values are β = 0.486 ± 0.021, γ = 1.068 ± 0.017 by the modified Arrott plot method, while β = 0.482 ± 0.008, γ = 1.060 ± 0.024 by the Kouvel–Fisher method. These values are close together and to those expected from the mean-field model, which reveals a long-range FM interaction in this alloy. [ABSTRACT FROM AUTHOR]

Magnetic properties, magnetocaloric effect, and critical behavior of Fe84-xCr2+xB2Co2Zr10 (x = 1, 2, 3, 4, 5, and 6) rapidly quenched alloy ribbons prepared by melt-spinning method have been investigated. X-ray diffraction analysis shows that the ribbons are almost amorphous. All the ribbons exhibit soft magnetic behavior with a low coercivity, Hc < 20 Oe. The magnetic phase transition temperature of the alloy can be adjusted in the room temperature region by appropriate Cr concentrations. With increasing Cr concentration, Curie temperature (TC) of the alloys is reduced from 330 K (for x = 1) to 290 K (for x = 6). The quite high maximum magnetic entropy change, |ΔSm|max > 0.8 J.kg−1.K−1 (under a magnetic field change of 12 kOe), and the wide working temperature range, δT > 90 K, around room temperature, have been achieved on these alloy ribbons. The obtained results reveal that Fe84-xCr2+xB2Co2Zr10 alloys are potential candidates for the magnetic refrigerants at room temperature region. Using the Arrott-Noakes method, critical analyses around the ferromagnetic-paramagnetic phase transition elucidated the magnetic orders in the alloys. The critical parameters determined for Fe84-xCr2+xB2Co2Zr10 ribbons are close to those of the mean-field theory applied for the long-range ferromagnetic orders. [ABSTRACT FROM AUTHOR]

• Structure and magnetic properties of Ni 50-x Co x Mn 50-y Al y rapidly solidified alloys. • Highly oriented column-shaped crystalline grains in melt-spun alloy ribbons. • Influence of concentration correlation of Co and Al on structural transformation. • Tuning structural transformation and magnetic transition of Ni-Co-Mn-Al alloys. • Influence of magnetic field on structural transformation and magnetic transition. Alloy ribbons of Ni 50-x Co x Mn 50-y Al y with x = 5–10 and y = 16–17 were prepared by rapidly solidified technique. Highly oriented column-shaped crystalline grains are observed in the alloy ribbons. The formation of martensitic (L 1 0) and austenitic (B2) phases and their structural transformation are strongly dependent on the concentration correlation of Co and Al. Co tends to enhance the fraction and the ferromagnetic interaction of the austenitic phase leading to a greatly increase of the saturation magnetization and Curie temperature of the alloy. The martensitic-austenitic (M−A) structural transformation process can be tuned to occur entirely above room temperature by appropriate concentrations of Co and Al. An irregular variation of the M−A transformation temperature happens in a narrow range, 8–8.5 at%, of Co concentration, while the ferromagnetic–paramagnetic (FM-PM) phase transition temperature monotonically increases. The external magnetic field favors the appearance of the austenitic phase and induces shifts to low and high temperatures for the M−A transformation and the FM-PM transition, respectively. [ABSTRACT FROM AUTHOR]