Warren E Pickett and Helmut Eschrig 2007 J. Phys.: Condens. Matter 19 315203 doi:10.1088/0953-8984/19/31/315203
Warren E Pickett1 and Helmut Eschrig2
Show affiliationsAt the basic level of collinear spin density functional theory, half metallic ferromagnets represent a fundamentally different state of matter: for low-energy physics the spin degree of freedom is absent, although the system is spin polarized. This makes such systems highly attractive for spintronics applications, but also introduces fundamental new phenomena such as a superconducting state in which the concept of 'spin-pairing' never appears. A fully relativistic theory introduces spin–orbit coupling and destroys the precise aspect of half metallicity; does this make 'half metals' a half truth? Obviously not in any real sense: spin–orbit coupling arises as a perturbative effect, and although necessitating reconsideration from the formal viewpoint, leaves half metallicity as a qualitatively distinct state. We provide a simple model that suggests that in appropriate circumstances this qualitative distinction may even survive strong spin–orbit coupling.
71.20.Gj Other metals and alloys
75.10.Lp Band and itinerant models
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
Issue 31 (8 August 2007)
Received 21 November 2006, in final form 23 January 2007
Published 3 July 2007
Warren E Pickett and Helmut Eschrig 2007 J. Phys.: Condens. Matter 19 315203
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