Title of Research Group: Magnetism and Spin Electronics

Principal Investigator: Prof. J. M. D. Coey

Institution: Trinity College Dublin

School: CRANN/AMBER & School of Physics

Research: The research of the group is focused on the growth and characterisation of new magnetic materials and their integration in demonstrator-like spin electronic devices. This includes structural, magnetic and transport properties of the materials, as well as the investigation of the interface between layers in multi-layered structures. High-brilliance neutron, x-ray and muon sources provide experimental techniques extremely useful for these studies, as they allow for the determination of both structural and magnetic properties at the atomic level, including interface.

Two examples of recent investigations below:
The properties of Mn-based alloys have attracted interest over the last ten years. We used a combination of bulk neutron diffraction with the XAS/XMCD (DEIMOS) analysis of the spin and orbital moments to determine the site-specific magnetic properties and origin of anisotropy in the tetragonal Mn3Ga. We were also able to infer, from K-edge EXAFS (SAMBA), the structure and order of a related alloy, cubic Mn2RuxGa, a material that exhibits high spin polarization along with a perfect magnetic compensation. Using XMCD (X’treme) we are currently determining the magnetisation of each sub-lattice, their dependence on x, and their exchange field.

In March 2014, we used the express service of GEM, ISIS; a new generation neutron diffractometer recently constructed at the pulsed neutron source. The GEM detectors in time of flight arrangement cover a scattering angle range from 1.1 to 169.3. Magnetic field up to 14T in 4-800K temperature range is also available. As the sample is heated through the magnetic ordering temperature, we were able to separate the magnetic contribution from the structural one and get a more complete picture of this material.

Techniques: XAS/NEXAFS/EXAFS, XMCD, XPS, Neutron diffraction

Facilities: SLS, SOLEIL, Orphée, ELBE, ISIS

Beamlines: DEIMOS, SAMBA, XTREME, FELBE, GEM

Group (as of 2014): 7Ph.D. and 6 PD
• Participating group members at SR/FEL/neutron facilities (period 2008-2014):

Ph.D. students Postdoctoral researchers
• Jonathan Alaria
• Marita O’Sullivan
• Karl Ackland
• Davide Betto
• Yong-Chang Lau • Hüseyin Kurt
• Zsolt Gerci
• Naganivetha Thiyagarajah
• Karsten Rode
Impact: Synchrotron radiation and neutron diffraction have allowed us to characterize the structural and magnetic properties of both bulk and thin film samples, including their interfaces. These studies have led to the discovery of new magnetic materials and modes, which may become useful in applications, and have also advanced the fundamental understanding of magnetism.

Quote: The experiments at SR light sources have been among the most interesting that I’ve ever done. The information obtained thanks to such high-level environments has been extremely useful for my research and the discussions with other researchers have been very valuable as well. “ – D. Betto

Publication Highlights:
• “Cubic Mn 2 Ga Thin films: Crossing the spin gap with ruthenium” DOI:10.1103/PhysRevLett.112.027201
• “Site-specific order and magnetism in tetragonal Mn3Ga thin films” DOI: 10.1103/PhysRevB.87.184429

Website: – Group Website