The magnetic and magnetocaloric properties of nanostructured CoMnGe0.95Ga0.05

• Published in: Journal of alloys and compounds Vol. 541; pp. 256 - 262
• Main Authors: Yüzüak, E., Durak, G., Dincer, I., Elerman, Y.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.11.2012; Elsevier
• Subjects: Alloys; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Entropy; Exact sciences and technology; Ferromagnetism; Magnetic fields; Magnetic properties and materials; Magnetic properties of nanostructures; Magnetization; Magnetization curves; Magnetocaloric effect; Martensitic transition; Nanomaterials; Nanopowders; Nanostructure; Physics; Magnetocaloric effect; Nanopowders; Martensitic transition; Magnetization; Doping; Magnetic field effects; Ferromagnetic materials; Magnetic hysteresis; Gallium additions; Magnetic refrigerators; Reverse martensitic transformations; Magnetocaloric effects; Fine grain structure; Nanopowder; Cobalt Manganese Germanides Mixed; Microstructure; Ferromagnetic-paramagnetic transitions
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2012.05.077

► The bulk shows a first order phase transition with huge hysteresis loses. ► Nanostructured has also phase transition with small hysteresis losses. ► Five hours milled powders should be a good candidate for the future applications. Evolution of magnetocaloric effect (MCE) of nanostructured CoMnGe0.95Ga0.05 powders has been investigated by electron microscopy (SEM), X-ray powder diffraction (XRD), thermal (DSC) and magnetization measurements. The nanostructured powders are composed of very fine grains (7±2 and 35±2nm) obtained from Rietveld refinements. The nanostructured powders show the unique ferromagnetic martensite–paramagnetic austenite transition around the room temperature like the bulk alloy. Furthermore, while the martensitic transition occurs in narrow temperature for bulk alloy, it occurs in broad temperature range for the nanostructured powders. The isothermal magnetic entropy change values −ΔSM are estimated from the isothermal magnetization curves. The maximum ΔSM values of 5h milled nanopowders are −7.2 and −21.5Jkg−1K−1 for a magnetic field change of 2 and 7T, respectively. The magnitudes of the MCE, magnetic and thermal hysteresis values of nanostructured powders are smaller than those of bulk alloy. Our findings offer the nanostructured CoMnGe0.95Ga0.05 powders for the promising applications in magnetic refrigeration.