The nature of the crystalline fields in Ti3+ alum

A theory of susceptibility for titanium caesium alum is given. The crystalline field in this alum is treated on the molecular orbital method of Stevens and others, as the usual electrostatic field theory is found to fail to explain the magnetic behaviour. Experimental susceptibility data between 300 and 100°K as well as the paramagnetic resonance data at 2·5°K can all be accounted for satisfactorily by assuming that the trigonal field splitting changes from 800 to ≈ 170 cm-1, with temperature, which is also indicated by the large observed increase in the spin-lattice relaxation time from 300 to 1·2°K.