[seminar] Podsjetnik na DANAŠNJI seminar na IF-u u 15:00h - Dr. Xavier Rocquefelte (Rennes)

[Damir Staresinic]

Institut za fiziku, Bijenička cesta 46, 

predavaonica u zgradi Mladen Paić ponedjeljak, 15. lipnja 2015., u 15:00 sati 
High-pressure cupric oxide: a room-temperature multiferroic 
Dr. Xavier Rocquefelte 
Institut des Sciences Chimiques de Rennes, Rennes, France 



Multiferroic materials [1], in which ferroelectric and magnetic ordering coexist, are of fundamental interest for the development of multi-state memory devices that allow for electrical writing and non-destructive magnetic readout operation. The great challenge is to create multiferroic materials that operate at room temperature and have a large ferroelectric polarization P. Cupric oxide, CuO, is promising because it exhibits a significant polarization,that is, P~0.1 μC/cm², for a spin-spiral multiferroic [2]. Unfortunately, CuO is only ferroelectric in a temperature range of 20 K, from 210 to 230 K. Here we propose an original theoretical investigation of the magnetic and ferroelectric properties of CuO under high pressure based on first-principles and Monte-Carlo calculations. We have established that pressure-driven phase competition renders CuO multiferroic at room-temperature [3-7], while preserving its large polarization and strong magneto-electric coupling. Moreover, under pressure values of 20-40 GPa the multiferroic phase becomes stable in a very broad temperature domain extending above 300 K (from 0 to T > 300 K). 









[1] Cheong, S. W. & Mostovoy, M. Multiferroics: a magnetic twist for ferroelectricity, Nature Mater. 6 , 13-20 (2007). 
[2] Kimura, T., Sekio, Y., Nakamura, H., Siegrist, T., Ramirez, A. P. Cupric oxide as an induced-multiferroic with high-T C , Nature Mater. 7 , 291-294 (2008). 
[3] Giovannetti, G. et al. High-T C Ferroelectricity Emerging from Magnetic Degeneracy in Cupric Oxide, Phys. Rev. Lett. 106 , 026401 (2011). 
[4] Rocquefelte, X., Schwarz, K. & Blaha, P. Comment on “High-T C Ferroelectricity Emerging from Magnetic Degeneracy in Cupric Oxide”, Phys. Rev. Lett. 107 , 239701 (2011). 
[5] Rocquefelte, X. et al. Short-range magnetic order and temperature-dependent properties of cupric oxide, J. Phys. Condens. Matter 21 , 045502 (2010). 
[6] Rocquefelte, X., Schwarz, K. & Blaha, P. Theoretical Investigation of the Magnetic Exchange Interactions in Copper(II) Oxides under Chemical and Physical Pressures, Scientific Reports 2 , 759 (2012). 
[7] Rocquefelte, X. et al. Room-temperature spin-spiral multiferroicity in high-pressure cupric oxide, Nature Communications 4 , 2511 (2013). 


Voditelji seminara IF-a: Nataša Vujičić i Damir Starešinić 




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