A Study Of Structure And Magnetic Properties Of The Sm₂（Co,M）₁₇ Rare Earth Compounds

The Sm₂Co_15.24-xFe_xCr_1.76（x=0.5，1.0，1.5，2.0，2.5）compoundsare prepared by means of arc smelting and high temperature quenching.The structure and magnetic of the compounds have been investigated byusing X-ray diffraction and Vibriting sample magnetometer. The powerX-ray diffraction patterns show that all samples crystallize in therhombohedral Th₂Zn₁₇-type structure with space group R-3m.Substitutionof Fe for Co does not lead to a change for crystal structure. The latticeparameters a、b and V increase monotonically with increasing Fe content，but the lattice parameter c is not changed much.All samples showeda-axis anisotropy at room temperature.The magnetic measurement resultsshow that the curie temperature T_C intends to decrease.The coercive forceis gradually reduced in easy axis direction and hard axis direction,but theremanence is increased.The Mn₅Ge_3-xCu_x（x=0.0,0.05,0.1,0.15,0.2） compounds are preparedby means of vacuum arc melting and high temperature annealing（850℃）.The structure and magnetic of the compounds have beeninvestigated by using X-ray diffraction and Vibriting samplemagnetometer.The power X-ray diffraction patterns show that all samplescrystallize in the rhombohedral Mn₅Si₃-type structure with space groupP63/mcm.When x=0.1,0.15,0.2,the compounds are present in a secondphase Mn₃Ge.Substitution of Cu for Ge does not lead to a change forcrystal structure, but the cell volume has been increased,which is due tothe Cu atomic radius is more than the atomic radius of Ge. The magneticmeasurements showed that the compounds showed a typical two phasetransitions.With the increase of Cu content, the Curie temperature remained unchanged,are295k.The value of the maximum magneticentropy change of the compounds decreases with increasing Cu content.