Objective
The goal of the project is to ascertain the interrelation between the anomalous physical properties, as giant spin fluctuation amplitudes, strongly enhanced thermal expansion in the paramagnetic range and frustrated magnetic structures, and microscopic characteristics of the d-electron system in various Mn compounds. The transport properties (electrical resistivity and thermopower), thermal expansion and magnetic susceptibility of various R-3d intermetallics with Mn (as RMn2, R6Mn23, RMn12, RMn2Ge2, RMn2Si2, -Mn etc.), will be measured in a wide temperature region 1.4900 K including the measurements under external pressure with the aim of determining the spin fluctuation contribution. In these studies the R-Mn intermetallics, which are expected to show a huge spin fluctuation contribution to the above characteristics, are of main interest. High field (up to 30) and low temperature magnetisation and magnetostriction measurements will complete the above measurements in order to follow the character of damping of the spin fluctuations by internal and external magnetic fields. The methodology of the work will be to study the magnetic, magnetoelastic and transport properties as a function of the following external parameters: external magnetic fields up to 30 T, external pressure up to 15 kbar, temperature in the range 1.5900 K. The internal parameters, density of d-states at the Fermi level, interatomic distances, stoichiometry and concentration, will be varied in a systematic way in order to reveal the interrelation between the internal (intrinsic) characteristics and external forces. The spin fluctuation dynamics will be studied by inelastic neutron scattering in the temperature interval 1.5290 K. As a result of these combined studies an improved picture of the spin fluctuation dynamics for itinerant magnets with a negative d-d exchange coupling will be developed, the character of damping of the spin fluctuations by nternal and external magnetic fields will be established. A new concept recently proposed by the applicants and based on the assumption of instability of the Mn electronic structure (an itinerant analogue of intermediate valency) will be verified.
Topic(s)
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1040 Vienna
Austria