Brought to you by PITP (www.pitp.phas.ubc.ca) Multiferroics for spintronics Manuel Bibes2 H. Béa1, M. Gajek1, X.-H. Zhu1, S. Fusil1, G. Herranz1, M. Basletic1, B. Warot-Fonrose3, S. Petit4, P. Bencok6, K. Bouzehouane1, C. Deranlot1, E. Jacquet1, A. Barthélémy1, J. Fontcuberta5 and A. Fert1 1 Unité Mixte de Physique CNRS / Thales, Orsay (FRANCE) 2 Institut d’Electronique Fondamentale, CNRS, Université Paris-Sud, Orsay (FRANCE) 3 CEMES, CNRS, Toulouse (FRANCE) 4 Laboratoire Léon Brillouin, CEA, Saclay (FRANCE) 5 ICMAB, CSIC, Campus de la UAB, Bellaterra (SPAIN) 6 European Synchrotron Radiation Facility, Grenoble (FRANCE) Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 1 Scientifique Ferroics and multiferroics Brought to you by PITP (www.pitp.phas.ubc.ca) Ferromagnetic materials Ferroelectric P Sensors E FeRAM Partially filled d/f shells M Magnetic Data Storage H Ferroelastic Spintronics Switchable parameter : M External stimulus : H Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 2 Scientifique Ferroics and multiferroics Brought to you by PITP (www.pitp.phas.ubc.ca) Ferroelectric materials P Lack of inversion symmetry Sensors E FeRAM M Magnetic Data Storage H Ferroelastic Ferromagnetic Spintronics Switchable parameter : P External stimulus : E Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 3 Scientifique Ferroics and multiferroics Brought to you by PITP (www.pitp.phas.ubc.ca) Multiferroic materials Ferroelectric P Lack of inversion symmetry Sensors E FeRAM Partially filled d/f shells M Magnetic Data Storage H Ferroelastic Ferromagnetic Spintronics From Spaldin and Fiebig, Science 309, 391 (2005) ~ Multiple-state memories Switchable parameter : M, P ~ M switching by E External stimulus : H, E ~ P switching by H Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 4 Scientifique Brought to you by PITP (www.pitp.phas.ubc.ca) Insulating oxides : a classification La0.1Bi0.9MnO3 NiFe2O4 BaTiO3 CoFe2O4 PZT EuO PbTiO3 BiMnO3 YMnO CoCr2O4 3 Tb Mn2O5 TbMnO3 BiFeO3 BiCrO3 Cr2O3 NiO PbZrO LaMnO3 3 LaFeO3 SrTiO3 MgO TiO2 ZnO Magnetically polarizable Electrically polarizable Magnetoelectric Ferro(i)magnetic Ferro(i)electric Derived from Eerenstein, Mathur and Scott, Nature 442, 759 (2006) Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 5 Scientifique Multiferroics - examples of magnetoelectric coupling Brought to you by PITP (www.pitp.phas.ubc.ca) (Gd,Dy,Tb)MnO3 : spiral magnets CoCr2O4 : conical magnet Spiral ordering breaks inversion symmetry Conical ordering breaks inversion symmetry Î (improper) ferroelectricity appears Î (improper) ferroelectricity appears (but no finite magnetization) (with a finite magnetization) Apply a magnetic field : change magnetic state Î switch polarization on/off Kimura et al, PRB 71, 224425 (2005) Flip polarization direction by a magnetic field Yamasaki et al, PRL 96, 207204 (2006) Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 6 Scientifique Brought to you by PITP (www.pitp.phas.ubc.ca) Insulating oxides : a classification La0.1Bi0.9MnO3 NiFe2O4 BaTiO3 CoFe2O4 PZT EuO PbTiO3 BiMnO3 YMnO CoCr2O4 3 Tb Mn2O5 TbMnO3 BiFeO3 BiCrO3 Cr2O3 NiO PbZrO LaMnO3 3 LaFeO3 SrTiO3 MgO TiO2 ZnO Magnetically polarizable Electrically polarizable Magnetoelectric Ferro(i)magnetic Ferro(i)electric Derived from Eerenstein, Mathur and Scott, Nature 442, 759 (2006) Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 7 Scientifique Brought to you by PITP (www.pitp.phas.ubc.ca) BiFeO3 A room-temperature antiferromagnetic ferroelectric Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 8 Scientifique Brought to you by PITP (www.pitp.phas.ubc.ca) BiFeO3 : bulk properties Rhombohedral Perovskite (R3c) a=3.96Å, α=89.4° Ederer et Spaldin, Phys. Rev. B, 71, 060401 (R) (2005) Neaton et al. Phys. Rev. B, 71, 014113 (2005) G-type Antiferromagnetic Ferroelectric TN=640K Canted spins weak FM TC=1100K → M =0.01µ /f.u. PS=6µC/cm² (1970 paper, bad crystal) S B J. R. Teague et al., Solid State Commun., 8, 1073 (1970) Incommensurate cycloidal modulation P. Fisher et al., J. Phys. C,13, 1931 (1980) PS=60µC/cm² (2007 paper, good crystal) D. Lebeugle, M. Viret et al, PRB in press Popov et al. in Magnetoelectric Interaction Pheno- Condmat/0706.0404 mena in Crystals (NATO Science Series, 2004) p. 277 Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 9 Scientifique Brought to you by PITP (www.pitp.phas.ubc.ca) BiFeO3 : thin films properties Wang et al., Science, 299, 1719 (2003) : BFO//STO (001) 3 t =200nm : P =55µC/cm² tBFO=70nm : MS=150emu/cm (~1µB/fu) BFO S 3 tBFO=400nm : Ms=5emu/cm (0.03µB/f.u.) Claim of enhanced polarization and magnetization compared to bulk Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 10 Scientifique Brought to you by PITP (www.pitp.phas.ubc.ca) Growth of BiFeO3 thin films 8 S S SS 10 B B tBFO=70nm B 6 B Pulsed laser deposition on SrTiO (001) 10 3 B 10-1 Target : Bi1.15FeO3 B 104 B B B B 6.10-3 Growth conditions : T=580°C, -3 B P =6.10 mbar 2 B O2 10 10-4 Tdep=580°C 8 Bi much more volatile than Fe : 10 SS St =70nm S BFO • low P or high T (Bi evaporates more than { { 6 Fe) 10 { B { 750°C ⇒ Fe oxides Intensity (counts) B B • high P or low T (excess Bi) 4 B 10 ⇒Bi oxides B 580°C B 2 B B 10 520°C P=1.2 10-2 mbar 20 40 60 80 100 2θ (°) B: BiFeO3, S: SrTiO3, *: γ-Fe2O3, |: α-Fe2O3, :Bi2O3 Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 11 Scientifique Brought to you by PITP (www.pitp.phas.ubc.ca) Growth of BiFeO3 thin films Phase diagram T (K) dep 1000 900 800 10-1 Pr ese P nce ure of Pure BiFeO obtained in a very BiFe BiO 3 -2 O x narrow region around T =580°C 3 dep 10 and P =6.10-3mbar P O2 rese nc e of Appl. Phys. Lett.,87, 072508 (2005) FeO -3 x P (mbar) 10 10-4 1,0 1,1 1,2 1,3 1000 / T (K-1) dep Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 12 Scientifique Brought to you by PITP (www.pitp.phas.ubc.ca) Growth of BiFeO3 thin films – Parasitic Fe-rich phases T (K) dep X-ray diffraction 1000 900 800 -1 10 Pre sen P ce 8 ure of B ) ) B ) ) ) iF iO 2 1 e 2 3 10 4 T=580°C -2 O x 0 0 0 0 0 ) 3 0 10 0 0 0 0 1 ( ( ( ( ( 0 P S 0 S B S S re 7 ( s e n ) ce 10 B o 3 ) f F 0 e 0 ) O ) ) 0 -3 0 ) 0 4 x ( 0 P (mbar) 4 0 2 10 0 ( 1 6 0 4 B -4 0 2 ( ( 8 F ( ( 10 P =10 mbar : F B O F F 2 5 120nm -4 10 10 -3 P =10 mbar : 1,0 1,1 1,2 1,3 O 4 2 -1 10 1000 / T (K ) 100nm dep 120 3 10 60nm 100 120nm Intensity (counts) Intensity 25nm 2 -4 2 1080 P=10-3mbar 10 25nm 60 20 40 60 80 100 40 B : BFO 2θ (°) S : STO Intensity (counts) Intensity (counts) F : γ-Fe2O3 1 10 20 92 93 94 94 96 95 96 98 97 100 98 102 99 22θθ (°)(°) Quantification of γ-Fe2O3 by XRD : not easily detectable Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 13 Scientifique Brought to you by PITP (www.pitp.phas.ubc.ca) Growth of BiFeO3 thin films – Parasitic Fe-rich phases SQUID measurements 150 ) 50 -3 P =10-3mbar : O2 75 25nm 40 60nm 100nm emu) -5 30 0 P =6 10-3mbar O2 120nm 20 -75 P =10-4mbar M (10 M (emu.cm O2 10 120nm Tdep=580°C -150 SQUID, 10K 0 -6 -4 -2 0 2 4 6 01234 γ-Fe O peak area (u.a.) H (kOe) 2 3 3 BFO + γ-Fe2O3 : up to Ms~150emu/cm Magnetic moment comes from γ-Fe O 3 2 3 γ-Fe2O3 ferrimagnetic (Ms=430emu/cm ) 3 Pure BFO : Ms~2emu/cm Phys. Rev. B, 74, 020101R (2006) BFO weak bulk-like ferromagnetic Similar conclusions : moment Eerenstein et al. Science, 307 1203a (2005) Wang et al., Science, 307, 1203b (2005) Centre National de Multiferroics for spintronics Manuel Bibesla Recherche Quantum Nanoscience with Spins, Asilomar 3-6 June, 2007 14 Scientifique Brought to you by PITP (www.pitp.phas.ubc.ca) (001) BiFeO3 films – Magnetic properties Neutron diffraction In R3c bulk BFO : * [003] H single peak → G-type antiferromagnet * [101] H peak with satellites → cycloidal modulation ⇒ Averaging to zero of the linear ME effect * * In pseudo-cubic notation : [003] H → [½ ½ ½] C * [101] H → [-½-½½]*C from Sosnowska et al., J. Phys. C, 15, 4835 (1982) BFO(240nm)//STO (001) ¾ G-type antiferromagnetic data 300 da ta fit order as in bulk BFO (a) 150 (c) fit simulated 250 peaks (SP) sum of SP ¾ No cycloidal modulation 200 100 contrary to bulk BFO 150 ¾ Linear magnetoelectric effect 100 50 IntensityIntensity (arb.