Etude des propriétés magnétostatiques et des structures magnétiques des chromites des terres rares et d'yttrium

The series of chromites TCrO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> (T = rare earth and Y) has been synthetized and investigated magnetically and by neutron diffraction. The Néel temperatures of the chromium spin ordering decrease with decreasing rare earth radius from θ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N1</inf> (La) = 282°K to θ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N1</inf> (Lu) = 112.4° K. The chromium spin configuration has a strong antiferromagnetic and a weak ferromagnetic component. The latter induces a measurable ferromagnetic polarization on the rare earth which sometimes shows occurrence of compensation temperatures (Gd, Tm). At low temperatures (<16° K) the rare earth orders as seen from susceptibility and neutron diffraction measurements. Susceptibility and magnetization data at high and low temperatures will be given and discussed. The different types of rare earth ordering observed by neutron diffraction at low temperatures will be discussed with special emphasis on the slacking fault type of spin disorder observed in TbCrO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> .