Nuclear magnetic ordering in Ca(OH)2. III. Experimental determination of the critical temperature
نویسنده
چکیده
2014 An experimental study of the magnetic ordering of the proton spin system in Ca(OH)2 is presented. The ordered phase is reached via dynamic nuclear polarization followed by an adiabatic demagnetization in the rotating frame. The spin temperature is negative while the external magnetic field is parallel to the crystalline c-axis. Measurements of the magnetization parallel to the effective magnetic field are used to determine the magnetic phase of the nuclear spin system. From a measurement of the energy of the nuclear spin system as a function of the entropy, the nuclear spin temperature is derived. The phase transition is found to occur at 0.9 03BCK, which is in good agreement with the theoretical prediction of the molecular field approximation. J. Phys. France 51 (1990) 1479-1488 1 er JUILLET 1990, Classification Physics Abstracts 75.30K 76.60
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