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Terahertz antiferromagnetic excitations driven by spin-current

Contact: CHAULEAU Jean-Yves, , jean-yves.chauleau@cea.fr, +33 1 69 08 01 42
Summary:
This internship deals with an assesment of the ultrafast properties of insulating antiferromagnets when subjected to different kind of stimuli (spin current, terahertz pulses…). The work will be focused on the use of a simulation code of atomic spin dynamics.
Possibility of continuation in PhD: Oui
Deadline for application:01/04/2019

Full description:
Among the ordered electronic states that occur in solid-state materials, magnetism is uniquely robust, persisting to well above room temperature in a wide variety of materials. Ferromagnets are now routinely used in the field of information technology. On the other hand, antiferromagnets (AF), which compose the overwhelming majority of magnetically ordered materials, have not been considered as candidates for active elements. In these materials, the magnetic moments of atoms align in a regular pattern with neighbouring spins pointing in opposite directions. Because of their zero net moment, antiferromagnets are rather insensitive to a magnetic field and difficult to probe. Thus, their intrinsic properties, and especially AF domains formation and the mobility of their domain walls, are poorly known.
In the last few years, it has been demonstrated that metallic antiferromagnets can lead to giant-magnetoresistance effects (resulting from spin-orbit-coupling), which validates their use as “spintronic elements”. On the other hand, insulating antiferromagnets are much more common than their conducting counterparts because super-exchange interactions in insulators are mainly antiferromagnetic. Direct control of AF properties requires unpractically large magnetic fields, not commonly available in a laboratory. The recent development of the spin transfer torque effect produced by spin polarized currents provides an ideal way of generating (the equivalent of) a staggered field, ideal to control the AF order. This should allow to toggle AF domains and influence the AF dynamical properties, but this has not yet been demonstrated.
The internship proposed here aims at studying the terahertz dynamics of the antiferromagnetic order when subjected to various stimuli, in particular picosecond spincurrent pulses. The work will be focus on the use of an atomic spin dynamics code in order to understand and master the underlying mechanisms of spincurrent-induced antiferromagnetic excitations. Ideally the internship should lead to a continuation as a PhD student.
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