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In this work we report on direct measurements of magnetocaloric effect in plastically deformed Gd-In solid solutions in the shape of foils with concentration of indium up to 3 at.%. When compared to the reference polycrystalline bulk samples, magnetocaloric effect in the cold-rolled foils of Gd 100− x In x ( x  = 0, 1, 3) turned out to be systematically smaller. This was suggested to be due to a cold rolling-induced local magnetic anisotropy which can be diminished by an appropriate thermal treatment of the cold-rolled samples. [ABSTRACT FROM AUTHOR]

• Demonstration of the new method of studding shape memory alloys in magnetic field. • Stress-temperature-magnetic field dependence for Ni 54 Mn 21 Ga 25 , Ni 50 Mn 41.2 In 8.8 alloys. • Ability of full recoverable deformation of ferromagnetic alloy in magnetic field. • Influence of magnetic field on the martensite transition temperature. • Bilayered functional composite of new type with enhanced properties. Recently the new scheme of layered composite with shape memory effect (SME) for thermal and magnetic actuation was suggested and proved to demonstrate the reversible actuation on micro- and nanoscale. The principles of magnetic field induced martensitic transition (MFIMT) and magnetic field controlled shape memory effect (MFCSME) have the advantages of magnetic-field-controlled actuation at constant temperature, extremely small size of an actuator and compatibility with modern nanotechnologies. The present paper is devoted to experimental study of MFCSME in two ferromagnetic Heusler alloys Ni 54 Mn 21 Ga 25 and Ni 50 Mn 41.2 In 8.8 with positive and negative shift of the martensitic transition temperature in a magnetic field. The three points bending device for dilatometric tests of plate-like samples of the alloys was designed and placed in the field of Bitter coil magnet. The bending deformations versus temperature were measured at various magnetic fields up to 10 T and at mechanical stresses up to 45 MPa. The temperature shifts of thermoelastic martensitic phase transition were found to be 0.55 K/T and −0.95 K/T for Ni 54 Mn 21 Ga 25 and Ni 50 Mn 41.2 In 8.8 respectively. For direct MFCSME study the dependences of the bending deformation on magnetic fields up to 14 T were also obtained at constant temperatures for these alloys. Practically complete recoverable deformation of 0.2% due to MFIMT was obtained at 14 T in Ni 54 Mn 21 Ga 25 alloy in temperature range 316–318 K and stress 8.6 MPa. The new variant of the layered functional composite actuator scheme based on the alloys with MFCSME is suggested. The proposed functional composite combines the layers of the alloys with positive and negative temperature shifts of martensitic transition temperature in magnetic field. It is argued that this combination of the alloys can improve the performance of the composite actuators driven by MFCSME, particularly, it can provide higher generated force, actuation stroke, sensitivity to magnetic field and frequency of actuation. [ABSTRACT FROM AUTHOR]

Highlights • Magnetocaloric effect (MCE) in cold rolled Dy was studied. • MCE in cold rolled Dy is reduced as compared to the bulk Dy. • Magnetocaloric properties of cold rolled Dy can be restored by annealing. Abstract We report on the magnetic properties and magnetocaloric effect of dysprosium ribbons obtained from a bulk sample by means of cold rolling. A magnetic entropy change Δ S ≈ 5.5 J/(kg·K) and an adiabatic temperature change Δ T ≈ 1.65 K for a bulk sample of dysprosium were observed for in external magnetic field changes of 3 T and 1.9 T, respectively. As compared to the bulk sample, Δ S and Δ T in the cold rolled ribbons is smaller by ∼30% and ∼12%, respectively. These changes in magnetocaloric effect of the cold rolled ribbons are fully reversible and can be restored by additional annealing. [ABSTRACT FROM AUTHOR]

Highlights • A method of preparation of FeNi L1 0 phase was proposed. • We applied cycling of oxidation/reduction processes at 320 °C of FeNi nanopowder. • This technique excels at up scaling and the ability to control the particle size. • Enhanced diffusion makes the synthesis of Fe-Ni alloys at low temperatures possible. • The influence of the synthesis parameters on physical properties was studied. Abstract FeNi L1 0 (tetrataenite) phase has great perspectives for hard magnetic materials production. In this paper we report on synthesis of this phase in chemically co-precipitated FeNi nanopowder by means of a thermal treatment procedure which includes cycling oxidation and reduction processes at 320 °C. The presence of the FeNi L1 0 phase in the samples was confirmed by magnetic measurements and differential scanning calorimetry analysis. [ABSTRACT FROM AUTHOR]

We report on the magnetocaloric effect in Gd 100- x B x ( x = 0, 10, 15) cold rolled ribbons. A moderate entropy change Δ S = 5 J/kg·K and adiabatic change of Δ T = 4.8 K were observed for the as-cast materials in an external magnetic field of 3 T which is less by 20% in comparison with the pure gadolinium metal. It was found that a significant (up to 70%) depression of magnetization and magnetocaloric properties developed in the course of plastic deformation can completely be restored by means of a high temperature heat treatment. It is concluded that cold rolling is one promising technique for producing foil shaped magnetocaloric materials suitable for designing heat exchangers of magnetic cooling devices. [ABSTRACT FROM AUTHOR]

• The effect of an external magnetic field on the dynamic and static properties of a highly anisotropic Ising antiferromagnet is studied. • It has been established that, depending on the magnitude of the magnetic field in the system, the realization of both dipole (FM) and more complex states (QU, LS) is possible. • The types of phase transitions are determined and the phase diagram is constructed for a strongly anisotropic Ising antiferromagnet as a function of the magnitude of the magnetic field. The effect of an external magnetic field on both the static and spectral properties of a highly anisotropic Ising antiferromagnet with magnetic ion spin S = 1 is studied. It is shown that at sufficiently low fields and large values of the single-ion anisotropy constant, a state with a zero value of the average magnetic moment (at the site), which is characterized by tensor order parameters (QU phase), is realized in the system. A further increase in the magnetic field turns the magnet (via a first-order transition) into the "quasi-ferrmagnetic" state. In this state is characterized by the fact that one of the sublattices is magnetized to saturation, whereas in the second the average magnetic moment (per site) is equal to zero. We called this phase the LS (low spin) phase. A further increase in the field leads to the realization of a ferromagnetic phase. All phase transitions are first-order transitions, as evidenced by the behavior of their spectra of elementary excitations. [ABSTRACT FROM AUTHOR]

Large exchange bias (EB) effect is demonstrated in a Ni 56 Mn 21 Al 22 Si 1 polycrystalline ribbon that shows spin-glass behaviour below 68 K and superparamagnetic (SPM) behaviour above this temperature. The average magnetic moment μ of the SPM clusters is estimated to be considerably smaller than that reported for other Heusler alloy systems that demonstrate spin glass behaviour and EB effect. The M – H loops measured in field-cooled (FC) conditions show significant asymmetry that is observed to be strongly field and temperature dependant. The maximum EB field ( H EB ~2.6 kOe at 20 kOe and 2 K) is much larger than that reported for any metallic alloy system with conventional EB effect. The dependence of H EB on temperature shows an exponential decrease. An approach towards enhancement of the EB effect in this conventional EB system can be realized via manipulation of SPM or superferromagnetic (SFM) cluster size with variation of cooling magnetic field. [ABSTRACT FROM AUTHOR]