Thulium magnetic measurements

Neutron diffraction measurements performed on a polycrystalline sample of TmCUjSij indicate that the compound is antiferromagnetic below the Neel temperature of 3.6 K. The magnetic structure is cosinusoidally modulated along the [110] direction with the propagation vector k = (0.147, 0.147, 0). The thulium magnetic moment of 5.1 makes an angle of 33(3)° with the c-axis (Allain et al. 1988). 

Initial measurements on thulium iron garnet TmlG, failed to observe all peaks in the spectrum [171], but later data gave values for the internal magnetic fields at the two thulium sites of 1700 and 810 kG at 20 K [172]. The fields are reduced from the free-ion value and that in Tm metal by anisotropic crystal-field and exchange interactions. 

Since the magnetic ordering temperatures of the oxides are generally low (on the order of liquid helium temperature), except for EuO, NGR experiments at higher temperatures can be expected to furnish only measurements of the quadrupole interaction and isomer shift. In the case of TmzOa, the Tm quadrupole interaction is strong and the spectra are so well-resolved that the interaction could be studied over a wide temperature range (up to almost 2000 K) [Barnes et al. (1964)]. The spacing of the Tm " crystal field levels responsible for the quadrupole interaction and its temperature dependence were derived from the measurements in the manner described for thulium metal in section 2.1.3. 

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