Publications | Diamond News Autumn 2009

Diamond News Autumn 2009

Studies put us on track for new magnetic phenomena and materials

 AFM image
Element-resolved images of a 2 micron-wide disk of IrMn(4 nm)/Ni80Fe20(5 nm) recorded by X-ray photoemission electron microscopy on beamline I06. The left and right image are representative of Fe and Mn in the top ferromagnetic and bottom antiferromagnetic layer, respectively. Black and white regions represent opposite magnetic contrast. The arrows indicate the curling of the magnetization in the vortex state.
Understanding the phenomenon of exchange bias is vital to continuing improvements in magnetic information storage. Exchange bias arises as thin layers of antiferromagnetic and ferromagnetic materials are superposed and magnetically coupled, which allows for finely controlling the behaviour of the ferromagnetic layer. Recently there has been considerable interest in laterally confined magnetic systems such as nanodots and microdisks.

An interesting magnetic configuration of such structures is the vortex state, characterized by an in-plane curling magnetization. Magnetic vortices are typical of ferromagnets; recently, several works have pointed out the possibility of inducing a vortex state in antiferromagnetic materials due to exchange bias. A group of scientists using the Nanoscience beamline (I06) have found direct evidence of imprinted vortex states in the anti-ferromagnetic layer with a reverse chirality pattern compared to the ferromagnetic layer. Their research, published in Applied Physics Letters, will help to understand the uncommon magnetic behaviour of such structures.

Prof. Pietro Gambardella, from the Institut Catala de Nanotecnologia (UA Barcelona) was part of the research team.

“We applied for beamtime at Diamond attracted by state-of-the-art equipment to perform magnetic spectroscopy and imaging using synchrotron radiation. From the first experiment during the commissioning of beamline I06 to the second one that led to our published results, we have found a continuously improving infrastructure and fully dedicated beamline team. We look forward to pursuing our search for new magnetic phenomena and materials at Diamond."

Prof. Pietro Gambardella, Institut Catala de Nanotecnologia

Direct evidence of imprinted vortex states in the antiferromagnet of exchange biased microdisks, G. Salazar-Alvarez, J. J. Kavich, J. Sort, A. Mugarza, S. Stepanow, A. Potenza, H. Marchetto, S. S. Dhesi, V. Baltz, B. Dieny, A. Weber, L. J. Heyderman, J. Nogués and P. Gambardella, Appl. Phys. Lett. 95, 012510 (2009)
DOI: 10.1063/1.3168515

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