Transcript Document
Rotation of the Pinning Direction in NiFe/FeMn bilayers X. P. Qiu , S. M. Zhou Department of Physics, Fudan University, Shanghai 200433, China Method to Identify the Pinning Direction (PD) Recovery Effect Exchange Bias (EB) 1 AFM my mx Steven Berems et al., PRL 95, 157202 (2005) Training Effect Hysteretic Behavior of EB 1st 2nd 20th HE HC 40 0 5 15 10 20 HC and HE decrease during consecutive sweep of hysteresis loops. 100 Magnetic Field (G) (a) 0 1st 20th -1 -400 -200 0 my (arb. units) 50 HE 40 200 (b) 0 -1 5 180 0 5 10 15 20 Cycle number n 360 Origin of the hysteretic behavior of EB FeNi single layer FeNi/FeMn bilayer 180 CCW CW PD (deg) 20 CCW CW 0 0 180 270 Dependence of ΔθPD on θH-Loop and tAFM Rotation of PD successfully explain the decrease of HC and HE in training effect of EB. Rtn (deg) 90 0 50 (a) 60 HE HC 40 (c) HE HC 40 30 20 20 10 30 0 (b) 30 10 1st 20th 0 (d) 15 0 -1 HC 20 Magnetic field (Oe) 1 (c) 60 PD(n) (deg) mx (arb. units) 1 my mx PD By rotating the sample in the film plane under zero magnetic field, the PD can be easily identified from the angular dependence of its magnetic moment. HE(C)/HE(C)(n=1) (%) HE(n), HC (n) (Oe) Correlation between Training effect and the Rotated Pinning Direction 0 Rtn (deg) PD (deg) HE(n), HC (n) (Oe) Moment (arb. units) Angular dependence of exchange bias shows hysteresis between clockwise and counterclockwise rotaions. 50 Cycle number n -300 -200 -100 ED (deg) H=0 60 0 20 10 0 0 (d) 20 10 0 -30 -60 H-Loop (deg) -90 0 1 2 3 4 5 6 tAFM (nm) Asymmetric Recovery Effect After training measurements, a magnetic field is applied at 900 or -900 (with respect to the initial PD) to recover the EB. 900 -900 900 ≠ -900! -20 45 HC (Oe) 10 5 -180 0 180 Schematic Explanation 30 15 -60 -30 H-Loop (deg) 0 HRE 30 60 H-Loop (deg) Initial PD PD oscillates around 00 ED only 00 or 1800 Rotated PD Spontaneous Recovery of PD 20 Rotated PD 15 PD (deg) HC (Oe) Moment (arb. units) FM Initial PD H Conclusion Pinning direction is identified and can be used to successfully explain the training effect, hysteretic behavior of angular dependence and recovery effect of exchange bias. Pinning direction is an important physical quantity in exchange bias. 10 5 0 0 24 48 72 Waiting Time (hours) 96 Reference: (1). Steven Brems, Dieter Buntinx, Kristiaan Temst, Chris Van Haesendonck, Florin Radu and Hartmut Zabel Phys. Rev. Lett. 95, 157202 (2005) (1).T. R. Gao, D. Z.Yang, and S. M. Zhou, R. Chantrell, P. Asselin, J. Du, X. S. Wu Phys. Rev. Lett. 99, 057201 (2007) (2). X. P. Qiu, D. Z.Yang, S. M. Zhou, R. Chantrell, K. O’ Grady, U. Nowak, J. Du, X. J. Bai, and L. Sun Phys. Rev. Lett. 101, 147207 (2008) (3). X. P. Qiu, Z. Shi, S. M. Zhou , J. Du, X. J. Bai, R. Chantrell and L. Sun J.Appl. Phys, 106, 063903 (2009)