Magnetic structure and anisotropy of YFe6Ga6 and HoFe6Ga6

The magnetic structure of RFe6Ga6 intermetallic compounds with R = Y, He ha ve been determined by neutron powder diffraction, Fe-57 Mossbauer spectrosc opy, AC susceptibility, TGA (Thermo-Gravimetric Analysis) and magnetization measurements. Both compounds crystallize in the tetragonal ThMn12 structur e (space group 14/mmm) with the magnetic structure of YFe6Ga6 consisting of a simple ferromagnetic alignment of Fe moments in the basal plane with a C urie temperature of 475(5) K. Gallium atoms are found to fully occupy the 8 i site, with Fe and Ga atoms equally distributed over the 8j site, whilst F e atoms fully occupy the 8f site. The average Fe moments are 1.68(10) mu (B ) and 1.46(10) mu (B) at 15 and 293 K, respectively. The average room tempe rature Fe magnetic moments determined by neutron diffraction are in overall agreement with the average Fe moment deduced from Mossbauer spectroscopy a nd bulk magnetization measurements on this compound. The magnetic anisotrop y of the compound HoFe6Ga6 is also planar in the temperature range 6-290 K, with Ho magnetic moments of 9.28(20) mu (B) and 2.50(20) mu (B) at 6 K and 290 K, respectively, coupled anti-ferromagnetically to the Fe sublattice a nd a Curie temperature of 460(10) K. The magneto-crystalline anisotropies o f both compounds are comparable at low temperatures.