Magnetic order and crystal structure study of YNi4Si-type NdNi4Si

• Below ~12 K the YNi4Si-type NdNi4Si shows a ferromagnetic ordering.
• MCE of NdNi4Si reaches value of –3.3 J/kg K in 0–50 kOe near Curie point.
• NdNi4Si exhibits b-axis ferromagnetic order with the Cmm′m magnetic space group.
• Contrary to CaCu5-type, YNi4Si-type NdNi4Si shows hysteresis loop at 2 K.

Magnetic measurements and neutron powder diffraction investigation of the magnetic structure of the orthorhombic YNi4Si-type (space group Cmmm) NdNi4Si compound are presented. The magnetocaloric effect of NdNi4Si is calculated in terms of the isothermal magnetic entropy change and it reaches the maximum value of –3.3 J/kg K for a field change of 50 kOe near TC=12 K. Below ~12 K, NdNi4Si exhibits a commensurate b-axis collinear ferromagnetic ordering with the Cmm′m magnetic space group in a zero magnetic field. At 1.5 K, the neodymium atoms have the magnetic moment of 2.37(5) μB. The orthorhombic crystal structure and its thermal evolution are discussed in comparison with the CaCu5-type compound.

The NdNi4Si supplement the series of the orthorhombic derivative of the CaCu5-type, namely the YNi4Si-type, RNi4Si compounds (R=Y, La, Ce, Sm, Gd–Ho). Below ~12 K in a zero applied magnetic field, NdNi4Si exhibits a commensurate b-axis collinear ferromagnetic ordering with the Cmm′m magnetic space group. Compared to the CaCu5-type NdNi4Si compound, the YNi4Si-type counterpart has the relatively high ferromagnetic ordering temperature (9.2 K vs. 12 K), the small magnetocaloric effect (–7.3 J/kg K vs. –3.3 J/kg K for ∆H=50 kOe), and the large magnetic anisotropy at low temperatures. In contrast with CaCu5-type NdNi4Si, YNi4Si-type NdNi4Si shows distinct hysteresis loop at 2 K.We suggest that orthorhombic distortion may be used as a prospective route for optimization of permanent magnetic properties in the family of CaCu5-type rare earth materials.Figure optionsDownload as PowerPoint slide