This study gives the temperature dependence of the Raman frequencies for the lattice mode of upsilon_7 (TA) and the internal mode of v2 close to the lambda-phase transition (T_(lambda)=234K, P=0) in NH_4Br. From the results obtained for temperature dependence of the Raman modes, the values of the critical exponent were extracted and compared with those for the thermal expansivity Op and for the specific heat Cp given in the literature. This is based on the assumption that the Raman frequency shifts exhibit critical behavior similar to those found in the thermal expansivity and the specific heat in the vicinity of the lambda-phase transition in NH_4Br.
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