Ph. D. position at LabEx MATISSE and SOLEIL Synchrotron

Laboratory: IMPMC, UMR7590, MIMABADI Addresse : IMPMC, Case 115, 4 place Jussieu, 75252 Paris cedex 05 Director of laboratory : Bernard CAPELLE Institution : CNRS/UPMC/IRD Ph.D. supervisor (HDR), téléphone et courriel : Philippe SAINCTAVIT Tel : 0144275065, email : Philippe.Sainctavit@upmc.fr Co-supervisors : Vincent Dupuis (PECSA), Philippe Ohresser (SOLEIL) Net salary : 1800 euros/month (36 months) Titre de la thèse: Magnetic Anisotropy of binary ferrofluids Description du projet: We study the magnetic anisotropies of binary ferrofluids for which macroscopic magnetic properties are governed by local, atomic anistropies. Ferrofluids are colloidal suspensions of nano-spinels (γ-Fe2O3,

MnFe2O4, CoFe2O4 with sizes between 5 and 20 nm) dispersed in a liquid (water, oil), famous for their various applications (mecanics, medecal applications, optics) and the spectacular instabilities they undergo under the influence of an external magnetic field (see videos by Kodama on YouTube) [1]. We know how to modulate the texturation of binary ferrofluides (orientation of easy axis of magnetization) by playing with temperature, and orientation/intensity of an external magnetic field. We aim at understanding the chaining between the nanoparticules of the binary ferrofluids with strongly different anisotropic nanoparticles : highly anisotropic versus weakly anisotropic nanospinels. The main experimental technique will be XMCD (X-ray Magnetic Circular Dichroism) at L2,3 and K edges of transition elements. The measurement shall yield direct and local, magnetic information on spin and orbit magnetic moments [2,3,4]. We should also be able to separate the magnetic contributions originating from nanoparticules with different magnetic anisotropy. The chaining geometry shall be determined as a function of temperature, magnetic field, and fluid viscosity. Among others the candidate will have to design and assemble an experimental UHV cell compatible with XMCD measurements of liquids. Techniques: XMCD at L2,3 and K edges of transition elements (Mn, Fe, Co et Ni) on DEIMOS@SOLEIL or ID12@ESRF beamlines. XMCD theoretical interpretation will use atomic theories (Ligand Field Multiplets) and/or solid state theories (Density Functionnal Theory). Requirements : The candidate should manisfest a sharp interest for experimental mesurements on synchrotron and for the instrumental developments required by XMCD. A good understanding of solid state physics, mainly magnetism, will be appreciated. The Ph.D. grant provided by LabEx MATISSE and SOLEIL is already availabale for September 2013 with accompanying extra-money for instrumental developments. [1]      R.   H.  Kodama,  Journal  of  Magnetism  and  Magnetic  Materials  200,  359  (1999)  et  S.  Kodama  http://www.youtube.com/watch?v=1W7dLRE3p-­‐4  [2]  M.  Mannini,  Ph.  Sainctavit  et  al.  468,  417,  2010  [3]  J.-­‐F.  Hochepied,  Ph.  Sainctavit  et  al.  Journal  of  Magnetism  and  Magnetic  Materials  213,  315-­‐322  (2001)  [4]  C.  Carvallo,  Ph.  Sainctavit  et  al.  American  Mineralogist  93,  880-­‐885(2008)