MOSSBAUER STUDY OF PARAMAGNETIC-LIKE BEHAVIOR BELOW THE NEEL TEMPERATURE IN A RANDOM MIXTURE FEXMN1-XTIO3 WITH X-LESS-THAN-0.3

As a part of studies of the microscopic behavior of spins in a mixed c ompound with competing exchange interactions FeMn1-xTiO3, the Mossbaue r technique has been applied to the samples with x = 0.05, 0.10 and 0. 20 which establish the antiferromagnetic long-range order at the respe ctive T(N)'s and do not show reentrant transitions at lower temperatur es. We have found that in each of the three samples, the paramagnetic doublet superimposes on the magnetically split spectrum below T(N). Th e peak intensity of die paramagnetic doublet decreases with decreasing temperature and the paramagnetic doublet becomes undetected as sharp peaks at a temperature around T(N)/2. However, the spectra observed at temperatures lower than T(N)/2 suggest that the paramagnetic doublet still exists, though it is highly broadened. This is interpreted as th at short-range clusters of spins fluctuating rather slowly with time c oexist with the spins forming the antiferromagnetic long-range order. We consider that these short-range clusters are responsible for the ex istence of the paramagnetic component contributing to the magnetizatio n versus temperature curve.