Nanoyapıdaki Ni50Mn34-Xcuxın16 (X= 1.3, 1.5) Heusler Alaşımlarının Manyetik Özelliklerinin İncelenmesi
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The aim of this study is to examine structural and magnetic properties of Ni50Mn34-xCuxIn16 (x = 1.3 and 1.5) Heusler alloys obtained for both bulk and ribbon and the magnetocaloric properties based on the results of the magnetic characteristics. It is expected that the magnetization and the martensitic transition temperatures increases if Ni50Mn34In16 Heusler alloy is doped with Cu atom replacing Mn atom. Bulk samples are produced from pure elements under argon atmosphere with water cooled copper crucible. Ribbon samples are produced in melt spinner system. The compositions of the bulk alloys are determined by using Scanning Electron Microscopy (SEM), EDX unit. The crystal structures of compounds are analyzed by using Rigaku Smartlab diffractometer with Cu radiation and Rigaku D-max 2200 diffractometer with Mo Kα radiation at room temperature. To find out the magnetic characteristics, Quantum Design Physical Properties Measurement System (PPMS) has been used. The structural and magnetic properties of the ribbon samples are performed by using Atomic Force Microscopy (AFM) and Magnetic Force Microscopy (MFM). According to x-ray diffraction experiments, bulk compounds have cubic structure (space group: F m -3 m) at room temperature and it has been observed that the Cu contribution has led to an increase in the unit cell parameter. By using atomic force microscopy, the approximate particle size is found to be 74 nm for Ni50Mn32.5Cu1.5In16 sample. According to the results of the rigidity analysis of the ribbon samples such as Ni50Mn32.7Cu1.3In16 and Ni50Mn32.5Cu1.5In16, the increasing of Cu has led to a decrease in the average porosity values. According to the results of the magnetic measurements for the bulk and ribbon samples, it has been observed that the alloys show both structural and magnetic phase transitions. For the bulk samples, the structural transition temperature increases with the increasing Cu concentration while it has been observed that the saturated magnetic values decreased. Based on the results of the magnetic measurements of the samples, the largest magnetic entropy change has been found for the Ni50Mn32.7Cu1.3In16 alloy. The magnetic entropy change for this alloy found to be about 47 J.kg-1.K-1 in a magnetic field of 7 T at 260 K. As for the magnetic measurements done on the ribbon samples, it has been observed that the saturated magnetization of the ribbon sample of Ni50Mn32.7Cu1.3In16 have been smaller than that of the bulk samples and the ribbon sample of Ni50Mn32.5Cu1.5In16. The structural transition temperature and magnetic entropy change for Ni50Mn32.5Cu1.5In16 ribbon sample were found to be lower than that of Ni50Mn32.5Cu1.5In16 bulk sample. According to the results of the magnetic force microscope measurements, the approximate magnetic domain size of the ribbon sample of Ni50Mn32.5Cu1.5In16 was obtained as 184 nm.