Low-Temperature Magnetic and Structural Transitions of the Quasi-One-Dimensional Magnets TMMC and DMMC at High Pressures

Abstract

The magnetic and structural phase transitions of the quasi-one-dimensional magnetic systems TMMC ((CH3)4NMnCl3; TN=0.84 K) and DMMC ((CH3)2NH2MnCl3; TN=3.60 K) have been studied by the heat capacity measurements at hydrostatic pressures. From the pressure dependence of the Néel temperature, the magnetic Grüneisen constant for the interchain interaction through –Mn– (CH3)4N–Mn– bridge has been conjectured to be much larger than 10 for the intrachain super-exchange interaction through –Mn–Cl3–Mn– bridge. A pressure-induced structural transition has been found in TMMC at pressure p=3.2±0.1 kbar at 4He temperatures. DMMC has been also suggested to experience a structural change in the range 3.2 kbar<p<3.7 kbar.