OPTICAL INVESTIGATIONS ON (N(CH3)4)2MNCL4 - A NEW PHASE-TRANSITION AT 90-K

The phase transitions undergone by [N(CH3)]2 MnCl4 crystals in the 10 - 300 K temperature range have been explored through the absorption and emission spectra as well as lifetime measurements. The present measurements confirm the existence of phase transitions at Tc3 = 268.7 K and Tc4 = 175.6 K and provide clear evidence of another (first order) phase transition at T5=£0K upon cooling and involving an hysteresis of AT = 12 K. The sensitivity of each of the optical parameters is studied for every phase transition. For the P2121/n phase transition the lifetime gives a small hysteresis ΔTc3 =0.4 K. © 1990, Taylor & Francis Group, LLC. All rights reserved.