Magnetism and antiferromagnetic spin density wave effects in Chromium and Chromium-based alloys
(from the left to the right) Ms Jabocs, Prof Prinsloo, Mr Gous, Dr Sheppard and Mr Muchono.
(from the left to the right) Mr Muchono, Dr Reddy and Prof Alberts.
Staff and students Involved
Chromium alloy systems exhibit a great variety of interesting antiferromagnetic properties that are associated with nesting of the Fermi surface sheets. The beauty of the properties of these materials originates in their spin-density-wave (SDW) state which contributes a large component, of magnetic origin, to nearly all their physical properties (Rev. Mod. Phys. Vol. 66 (1994)25). What makes these materials more attractive is the fact that, due to the large contribution of SDW origin to their physical properties, once the fundamental role of the SDW in these properties is understood, one can tailor the alloys to give physical properties, like particular thermal expansion, elastic constants, electrical resistivity, etc., that can be useful in practical applications. Significant innovation will be the role of dimensionality effects in the properties of Cr and its alloys through the studies on magnetic thin films. There is renewed interest in the literature in the physical properties of dilute Cr alloys, particularly in their magnetic phase diagrams and more recently in the quantum critical point effects in dilute Cr alloys (Phys. Rev. B69 (2004) 144423), in studies on single crystalline alloys, in their anharmonic effects and in their role as spacer layers in magnetic multilayer thin film structures with giant magnetoresistance properties (J. Magn. Magn. Mat.: "Magnetism beyond 2000", Vol. 200, no.'s 1-3 (1999) for the latter). The magnetic multilayers are of interest not only for their scientific value, but also since specific magnetic properties can be "designed" in such artificially structured materials.
Our studies are aimed at gaining insight and understanding into the unique effects of the spin-density-wave on the physical properties of chromium and its alloys, both in bulk and thin film forms. It includes investigations of magnetoelasticity and anharmonic effects, Invar and Elinvar properties, electrical transport properties, magnetic susceptibility, specific heat, superconductivity and magnetic phase diagrams of Cr alloys, as well as spin-density-wave effects in Cr alloy thin films and in multilayers with Cr alloy spacer layers. The magnetism group has a well equipped laboratory available for studying magnetic properties of materials, including the following: arc furnace for alloy preparations, crystal growing equipment (Bridgman, Czochralski, floating zone), spark cutting equipment, ultrasonic measuring equipment (phase comparison and pulse-echo-overlap methods) for ultrasonic velocity and attenuation measurements, equipment for accurate electrical resistivity, thermal expansion, magnetic susceptibility, thermal conductivity and Hall effect measurements, X-ray equipment, high pressure (0-14 kbar) and low to high temperature (4K-1000K) equipment. Electron microprobe, XRD, SEM and AFM equipment, are used regularly in our projects and neutron diffraction studies are done at Necsa.
Collaboration exists with the following research groups: Prof AM Strydom at University of Johannesburg, South Africa (on low temperature measurements); Dr AM Venter at Necsa, South Africa (on neutron diffraction); Dr D Spenato at University of Brest, France; and Prof EE Fullerton at UCSD, USA (on thin magnetic films).
As the studies involve high technology experimental techniques and highly advanced theories in magnetism and physics in general, the level of the research requires the highest academic standards of exceptional quality. Our previously published work on Cr alloys and Cr alloy thin films (see for instance our publications: Phys. Rev. B56 (1997) 11777 and Phys. Rev. Lett. 91(23) (2003) 237201) speaks for the high academic standards and quality. This project has been running for more than two decades under the guidance of Prof HL Alberts and a number of 118 (of which 25 was co-authored by Prof ARE Prinsloo) were published in peer reviewed scientific journals.
The research is ideally suited for training of MSc and PhD students of the highest quality. The project has already delivered 12 MSc students and 6 PhD students. The high quality of training is attested by the fact that 7 prizes have been won by various students involved in this project for presentations and publications emanating from their research work.
Research Highlights