+ M onezuelo Electric field Magnetic field ferroelectics(P) ferromagnet(M) ↑ electric field ◆magnetic field multiferroics (Px M) Magnetic field Electric field
國 Multiferroicity: Our experiences beyond manganites J.-M.Liu(刘俊明) Nanjing University Email:liujm@nju.edu.cn Group page http://pld.nju.edu.cn/
J. –M. Liu ( M. Liu (刘俊明) Nanjing University Nanjing University Email: liujm@nju.edu.cn liujm@nju.edu.cn Group page Group page http://pld.nju.edu.cn/ //pld.nju.edu.cn/ Multiferroicity: Our experiences beyond manganites
R1-xAx MnO3 多ma8ogo (disorder Metal Metal A 3z2-2 Insulator A ● C G 3x2.213y2-2 Insulator Nd CE ■ CxE1-x 0.2 0.4 0.6 ….0.8 hole concentration X Y.Tokura,RPP69,797 (2006)
Y. Tokura, RPP69, 797 (2006)
Content >Background motivations Origin of spiral spin order in manganites >Predictions of novel multiferroics >Phase competition and beyond Exchange bias in multiferroic heterostructure Summary perspectives
Content Background & motivations Origin of spiral spin order in manganites Predictions of novel multiferroics Phase competition and beyond Exchange bias in multiferroic heterostructure Summary & perspectives
Background:symmetry argument Magnetism Ferroelectricity Partially filled d shells Empty d shells break break Time reversal Space reversal symmetry symmetry t-→-t,M→-M x→-x,P→-P H-f(M,P)=f(-M,-P)=f(-M,P)=f(M,-P) N.A.Hill,Why are there so few magnetic ferroelectrics?J.Phys.Chem.B 104:6694(2000)
Background: symmetry argument ++ - ++ Partially filled d shells break Time reversal symmetry t-t, M-M N. A. Hill, Why are there so few magnetic ferroelectrics? J. Phys. Chem. B 104: 6694 (2000). Empty d shells break Space reversal symmetry x-x, P-P Magnetism Ferroelectricity H=f(M, P)=f(-M, -P) = f(-M, P)=f(M, -P)