Magnetic structure of Nd 7Co 6Al 7

Abstract

Time-of-flight neutron powder diffraction has been used to determine the magnetic structure of the intermetallic compound Nd 7Co 6Al 7. The thermodynamic, magnetic and electrical properties of this compound indicate that it undergoes a paramagnetic–ferromagnetic transition at 15.5 K, and possesses a magnetic refrigerant capacity of approximately 40 J/kg. The average value of the high field saturation magnetic moment per Nd atom at low temperatures is almost 50% below that of the free ion value. Neutron powder diffraction measurements have been performed at 300 K, in order to confirm the details of the crystal structure, and below the magnetic ordering temperature, at 6 K, in order to establish the nature of the magnetic structure. The high temperature data clearly confirm that Nd 7Co 6Al 7 crystallizes in the Pr 7Co 6Al 7 structure (space group P4/ mbm). The low temperature data show the presence of reflections at (100), (110), (200) and (210), reflections which are non-existent above the ordering temperature. The presence of the (100) reflection indicates the presence of antiferromagnetic configurations in this system. Models of the magnetic structure for Nd 7Co 6Al 7 will be presented and discussed.