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Ultrasonic frequency shifts close to the first order and tricritical phase transitions in NH4Cl

2001-12-01
Yurtseven, Hasan Hamit
Tari, O
Bas, M
This study examines our spectroscopic modifications of the Pippard relations using the ultrasonic frequencies of the q[110] and q[1 (1) over bar0] modes for the first order phase transition in NH4Cl. We also examine our relations using the ultrasonic frequencies of the q[110] mode for the tricritical phase transition in this crystal. From our plots of the specific heat C-p as a function of the frequency shifts (1/nu)(partial derivative nu/partial derivativeT)(p), we obtain that our spectroscopically modified Pippard relation considered here is satisfied for those phonon modes studied close to the first order and tricritical phase transitions in NH4Cl.