Pressure effects of genuine organic crystalline ferromagnet possessing intermolecular contacts between nitroxide oxygen and methyl hydrogen atoms

We have found the pressure-induced (1) periodical down-up variation of tran sition temperature (T-c), (2) ferro- to antiferro-magnetic transition and ( 3) reduction of the magnetic lattice dimensionality in a genuine organic cr ystalline bulk-ferromagnet p-Cl-C6H4-CH=N-TEMPO (T-c = 0.28 K) with spin po larizations on intermolecular contacts between the nitroxide oxygen and met hyl hydrogen atoms (C-H . . .O-N contacts). These phenomena can be understo od by the pressure-induced rotation of the methyl moiety relevant to the in teraction-mechanism through C-H . . .O-N contacts. (C) 2001 Elsevier Scienc e B.V. All rights reserved.