Skip to Main content Skip to Navigation
Theses

Matériaux moléculaires et composé à fermion lourd : ferromagnétisme et antiferromagnétisme, effets de dimensionnalité , transition de phase et phénomène d'avalanche

Abstract : We present an experimental study of the magnetic properties of the spin chain (R) • 3MLNN Mn(hfac)2 at very low temperatures. The magnetic carriers are Manganese Mn +II with spin 5/2 and Nitronyl-nitroxide radicals with spin 1/2. The compound has 1D ferrimagnetic beha-viour at high temperature. Near 20 K, we observe a 1D-3D crossover. At Tc = 3 K, an unusual phase transition occurs. Above Tc , ferromagnetic behaviour is observed, with Heisenberg critical exponents. Below Tc, a canted antiferromagnetic structure appears. In the ordered regime, dynamic measurements show an energy barrier of 15.5 K. Below 250 mK, avalanches occur during hysteresis loops at an intrinsic field H = 170 Oe. We postulate that these properties may be related to the nucleation of one dimensional domain-walls on the chains. We make a com-parison with two other systems which also show avalanches: the spin chain CoT AC and the heavy fermion UGe2 . Measurements were made using two SQUID magnetometers equipped with miniature dilution refrigerators developed at the CRTBT-CNRS.
Document type :
Theses
Complete list of metadatas

https://tel.archives-ouvertes.fr/tel-00008219
Contributor : Nathalie Le Moulec <>
Submitted on : Friday, January 21, 2005 - 10:29:52 AM
Last modification on : Friday, November 6, 2020 - 3:49:21 AM
Long-term archiving on: : Friday, April 2, 2010 - 9:02:08 PM

Identifiers

  • HAL Id : tel-00008219, version 1

Collections

UJF | CNRS | UGA

Citation

Elsa Lhotel. Matériaux moléculaires et composé à fermion lourd : ferromagnétisme et antiferromagnétisme, effets de dimensionnalité , transition de phase et phénomène d'avalanche. Matière Condensée [cond-mat]. Université Joseph-Fourier - Grenoble I, 2004. Français. ⟨tel-00008219⟩

Share

Metrics

Record views

311

Files downloads

2133