Energy barrier measurement and optimization in exchange coupled FePt/TiO2 nano-composite thin films

Abstract The 45-degree method is firstly applied to measure the energy barrier of FePt/TiO 2 nanocomposite thin films with hard layer only and with hard–soft coupled bilayers. It was experimentally demonstrated that energy barrier measured using 45-degree method is more reliable than that measured using the conventional method with which the field is applied along the film normal. It is found that the energy barrier of bilayer films decreases with soft layer thickness, while the interlayer exchange coupling has little effects on the energy barrier. Both soft layer thickness and interlayer coupling strength have a strong effect on the figure of merit. Decrease in interlayer coupling firstly increases the figure of merit, while, too much reduction of coupling results in the appearance of 2-step switching and therefore decreasing in figure of merit.

[1]  R. Victora,et al.  Predicted time dependence of the switching field for magnetic materials. , 1989, Physical review letters.

[2]  D. Suess.  Micromagnetics of exchange spring media: Optimization and limits , 2007 .

[3]  Dieter Weller,et al.  Extremely High-Density Longitudinal Magnetic Recording Media , 2000 .

[4]  D. Weller,et al.  Development of Co-alloys for perpendicular magnetic recording media , 2003, Joint NAPMRC 2003. Digest of Technical Papers.

[5]  H. Bertram,et al.  Energy Barriers in Composite Media Grains , 2007, IEEE transactions on magnetics.

[6]  J. W. Harrell.  Orientation dependence of the dynamic coercivity of Stoner-Wohlfarth particles , 2001 .

[7]  D. Weller,et al.  Thermal energy barrier distribution measurements in perpendicular media , 2002 .

[8]  Jianping Wang,et al.  Exchange coupled composite media for perpendicular magnetic recording , 2005, IEEE Transactions on Magnetics.

[9]  T. Schrefl,et al.  Reliability of Sharrocks equation for exchange spring bilayers , 2007 .

[10]  O. Heinonen,et al.  Extensions of perpendicular recording , 2008 .

[11]  Y. Lu,et al.  A silicon microactuator using integrated microfabrication technology , 2003, Digest of INTERMAG 2003. International Magnetics Conference (Cat. No.03CH37401).

[12]  D. Weller,et al.  Magnetic anisotropy and thermal stability study on FePt nanoparticle assembly , 2003 .

[13]  Y. Peng,et al.  Magnetic cluster size and cluster size distribution study on perpendicular media , 2008 .

[14]  Koki Takanashi,et al.  Coercivity exceeding 100 kOe in epitaxially grown FePt sputtered films , 2004 .

[15]  S. Liou,et al.  Fabrication of nonepitaxially grown double-layered FePt:C/FeCoNi thin films for perpendicular recording , 2003 .

[16]  Thomas Schrefl,et al.  Exchange spring media for perpendicular recording , 2005 .

[17]  D. Suess.  Multilayer exchange spring media for magnetic recording , 2006 .

[18]  Evaluation of 45° method in characterizing the anisotropy of the perpendicular media , 2007 .

[19]  H. Miyajima,et al.  Simple analysis of torque measurement of magnetic thin films , 1976 .

[20]  Jian-Ping Wang,et al.  In situ ordering of FePt thin films with face-centered-tetragonal (001) texture on Cr100−xRux underlayer at low substrate temperature , 2002 .

[21]  Olle Heinonen,et al.  Read and write processes, and head technology for perpendicular recording , 2009 .

[22]  J.Lee,et al.  Exchange-coupled perpendicular media , 2009 .

[23]  M. Sharrock,et al.  Time dependence of switching fields in magnetic recording media (invited) , 1994 .

[24]  H.J. Richter,et al.  Domain Wall Assisted Magnetic Recording , 2006, INTERMAG 2006 - IEEE International Magnetics Conference.

[25]  T. Zhou,et al.  Anisotropy graded FePt-TiO2 nanocomposite thin films with small grain size , 2009 .