Correlation between structure and magnetism in thin films INFM, Unità di Genova Francesco Bisio

Experimental techniques: Magnetism+ structure in situ MOKE + MSHG, Polar+longitudinal QLEED UHV chamber:p~1.5· mbar; Electromagnet ~800 Oe; MOKE: 670 nm laser diode; SHG: Ti:sapphire 720÷880 nm, <100fs pulse. viewport sample Phosphor- screen Magnet LEED Laser 670 nm viewport polarizer Monochr. PMT

sample Magnet Magnetism + Structure: Fe/Cu 3 Au T=185 K SRO Onset of Magnetic order POLAR Magnet sample Magnet LONGITUDINAL SRO T=290 K sample Magnet LEED (00) (11)

Fe/Cu 3 Au thin films Fcc substrate, a=3.745 Å Possibility of stabilising metastable Fe structures Possible coexistence of different structural phases within the same film AF NM FM P. M. Marcus et al. PRB 60, 369 (1999) R ws (a. u.) Fcc Fe: Magnetic properties depend upon lattice parameter (110) (100) (-110) a=2.65 Å c/a= 2 Au Cu Fe

Fe / Cu 3 Au: structural properties Intensity [a. u.] Bcc Fe R45° H [r. l. u.] Substrate, Pseudomorphic Fe F. Bruno et al. PRB 66, GIXRD radial scans vs. film thickness

Structure and morphology ~150 Å thk >30 Å Low coverage: thk<10 Å Medium coverage: 10 Å<thk< 20 Å High coverage: thk>25 Å Fe substrate Fe substrate Fe substrate Fe

Structure-magnetism correlation Cu 3 Au Cu 3 Au Cu 3 Au T dep ~295 K Hext=± 50 Oe Hext|| (100) M M M Optical – Magneto Optical response ? Interface hybridization ? Different per atom ?

Morphology-magnetism correlation T dep ~295 K Hext=± 50 Oe H ext || (100) T dep ~295 K Hext=± 50 Oe H ext || (110)

Morphology-magnetism correlation H ext || (100) H ext || (110)

Temperature dependence of magnetic properties Morphological effect Intermixing + Curie temperature shift Kerr asymmetry during growth vs. substrate temperature

People Università di Genova e UdR INFM G. Gonella R. Moroni S. Terreni M. Canepa L. Mattera

Conclusions Experimental apparatus devoted to the study of structure-magnetism correlation; Application to heteroepitaxial ultrathin magnetic films; Study of buried interface properties (MSHG); Dependence of magnetism upon crystallographic parameters;

sample Magnet LEED Experimental techniques: real time MOKE T=185 K SRO Onset of Magnetic order POLAR Fe/Cu 3 Au sample Magnet LEED LONGITUDINAL SRO T=290 K Fe/Cu 3 Au

Intensity [a. u.] H [r. l. u.] Fe/Cu 3 Au: structural properties Coexistence of multiple structural phases on the film In-depth scan of the film