engleski

Unusual magnetic field-induced transition in the low temperature (T<1K) SDW ground state of (TMTSF)2PF6

It is now well known that the (TMTSF)2PF6 salt exhibits an unconventional SDW ground state below T* 4 K. For instance, the heat capacity in this state becomes dominated by extra- phononic excitations with two contributions: a Schottky anomaly predominant below 0.3K, and a quasi-linear contribution up to 1K. The latter one is ascribed to the disordered character of the pinned SDW (glassy state) below T*. In addition, strong heat release phenomena also reminiscent of structural glasses, occur in this low T-range. We report here on a magnetic field study of both of these coupled thermal properties. Below 0.5K, these two properties are strongly sensitive to moderate magnetic fields ( lower than 0.5 T): their amplitudes show a sharp maximum at H=HC= 0.2 T. The effects are independent of the field orientation compared to that of the crystals ( H // a, or H // b’ axis). We conclude that the sharp amplitude maximum is essentially related to the variation of that of the Schottky anomaly, i.e. to NS, the corresponding density of two-level states. This unexpected large variation – by a factor of 3 -of NS under field rules out an extrinsic origin. Instead, we suppose an intrinsic origin, such as defects of commensurability of the SDW, at the origin of glassy behaviour. The sharp discontinuities suggest a field induced phase transition of the SDW at H=HC. The paper is available at: J. Low Temp. Phys.(2003), in the press: S.Sahling, J.C.Lasjaunias, K.Biljakovic, P.Monceau “ Magnetic Field Influence on the Low Temperature Heat Capacity and Heat Release of (TMTSF)2PF6 “

spin density waves ; magnetic field ; transition

nije evidentirano