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Magnetic properties and magnetocaloric effect of the ferrimagnetic compounds Gd4Co3 and (Gd0.9Dy0.1)4Co3 have been studied. In Gd4Co3, two successive magnetic-entropy changes occur due to a spin-reorientation transition at TSR=163 K and a ferrimagnetic-magnetic ordering transition at TC=220 K. For a field change from 0 to 5 T, -ΔSMmax at TC is 5.74 J/kg K, the full width at half maximum (δTFWHM) of the -ΔSM versus T curve has a high value of 131 K, and the refrigerant capacity is as high as 575 J/kg. TC can easily be tuned by Dy substitution for Gd and the magnetic-entropy change is increased simultaneously. -ΔSMmax of (Gd0.9Dy0.1)4Co3 at TC=145 K for the same field change has increased to 8.47 J/kg K. Our studies suggest that the successive magnetic transitions could enlarge the temperature interval, which makes this type of material meaningful for magnetic refrigeration in wider temperature regions than conventional materials. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect associated with magnetic phase transitions in β-Co(OH)2 nanoparticles has been investigated. A sign change in the magnetocaloric effect is induced by a magnetic field, which is related to a field-induced transition from the antiferromagnetic to the ferromagnetic state below the Néel temperature. The large reversible magnetic-entropy change -ΔSm (20.9 J/kg K at 15 K for a field change of 7 T) indicates that β-Co(OH)2 is a potential candidate for application in magnetic refrigeration in the low-temperature range. [ABSTRACT FROM AUTHOR]

A large reversible negative magnetic-entropy change ΔSM has been observed in TbCoC2, accompanied by a second-order phase transition at 28 K. The maximum value of -ΔSM is 15.3 J kg-1 K-1 at 30 K for a magnetic-field change from 0 to 5 T, with the refrigerant capacity of 354 J kg-1. In particular, also the large -ΔSMmax of 7.8 J kg-1 K-1, is obtained for a small field change from 0 to 2 T. The large reversible ΔSM and the high reversible refrigerant capacity in low magnetic field indicate that TbCoC2 may be a promising candidate for magnetic refrigeration at low temperatures. [ABSTRACT FROM AUTHOR]

The spin orientation and spontaneous magnetostriction of multicomponent TbxDy1-x-yPry(Fe0.9B0.1)1.93 (0.10 ≤ x ≤ 0.25, 0.30 ≤ y ≤ 0.60) Laves phases were studied by step-scanning their (440) X-ray diffraction lines. The easy magnetization direction (EMD) of the, Laves phases changed from the «100» to «111» axis when x was increased from 0.10 to 0.25. With increasing y, the EMD of Tb0.15Dy0.85-yPry(Fe0.9B0.1)1.93 and Tb0.2Dy0.8-yPry(Fe0.9B0.1 )1.93 Laves phases `reoriented from the «100» to «111» axis. The magnetostriction coefficient λ111 of TbxDy1-x-yPry(Fe0.9B0.1)1.93 Layes phases increased with increasing x (or y) when y (or x) was kept constant. [ABSTRACT FROM AUTHOR]

The effects of B and C substitution for Sn on phase components, Curie temperature TC, and magnetocaloric effect of melt-spun Mn3Sn2-xMx (M = B, C; x = 0-0.5) ribbons have been investigated. X-ray diffraction (XRD) results show that the main phase in the as-spun Mn3Sn2-xMx (M = B, C; x = 0-0.5) ribbons is Mn3Sn2 of Ni3Sn2-type (Pnma). Minor Mn2B (when x ≥ 0.1) or Mn5C2 (when x > 0.1) secondary phase is formed, and their amounts increase with increasing B and C concentration, respectively. The Curie temperature TC of these ribbons varies in the temperature range of 240-250 K. The peak values of the maximal magnetic entropy change, -ΔSMmax, are about 13.6-18.3 mJ/cm3 K for B-substituted ribbons and 13.6-17.5 mJ/cm3 K for C-substituted ribbons, respectively, at a maximum applied field of 50 kOe. These values are about one fifth that of Gd (81.4 mJ/cm3 K). However, the relatively broader temperature range of the half maximum of ΔSM peak (∼100 K), low-cost and nontoxic elements still make Mn3Sn2-based ribbons the promising candidates for magnetic refrigeration applications close to room temperature. [ABSTRACT FROM AUTHOR]

The effects of Si substitution for Al on the glass forming ability, Curie temperature TC, magnetocaloric effect, and refrigeration capacity (RC) of melt-spun Gd-based Gd65Fe20Al15-xSix (x = 0-7) glassy ribbons have been investigated. The small amounts of Si substitution for Al in the Gd65Fe20Al15-xSix glassy ribbons with high Tx/Tm (> 0.70) and small ΔTm (ΔTm = Tm-Tx) promote the formation of high thermal stability of these alloys. The Si addition leads to an increase of Curie temperature TC of glassy ribbons from 181 K for x = 0 to 227 K for x = 7. The maximal magnetic entropy changes -ΔSM and RC values for magnetic field change of 50 kOe are about 4.70-5.20 J/kg K and 710-760 J/kg, respectively. The large RC values are due to the broad temperature range of the half maximum of ΔSM peak (∼ 200 K), which is caused by the change of the amorphous disorder structure. The moderate ΔSM and large RC values jointly make the Gd65Fe20Al15-xSix glassy ribbons promising candidates for magnetic refrigeration materials working at temperature range of 100-300 K. [ABSTRACT FROM AUTHOR]

Reports on the measurements of the structure, magnetic properties and magnetostriction of arc-melted polycrystalline alloys. Methods employed to measure the properties; Number of arc-melted samples prepared for the experiment; Magnetic field dependence of magnetization for the alloys at room temperature.