Magnetisation reversal of thin submicron elliptical permalloy elements

We have studied the magnetisation reversal of elliptical, polycrystalline permalloy elements as a function of their aspect ratios by Lorentz transmission electron microscopy. In situ magnetising experiments revealed four possible types of magnetisation reversal, which depend on the in-plane and out-of-plane aspect ratios of the submicron elements. The types differ in the number of observed vortices and a low or high remnant magnetisation. Diagrams of the types of magnetisation reversal are given for submicron elliptical elements of length 350, 550, 750 nm and a thickness of 8 and 15 nm, respectively. The switching, vortex evolution and annihilation fields were investigated and show a strong correlation with the element shape. We present magnetisation loops which are obtained by micromagnetic simulations and are characteristic for the observed types of reversal.

[1]  Jian-Gang Zhu,et al.  Magnetization vortices and anomalous switching in patterned NiFeCo submicron arrays , 1999 .

[2]  E. Schlömann,et al.  Demagnetizing Field in Nonellipsoidal Bodies , 1965 .

[3]  S. Tehrani,et al.  Switching anomaly and magnetization vortices of 200 Å thick NiFeCo elements in one-micron patterned arrays , 1999 .

[4]  M. Rahm,et al.  Switching behavior of vortex structures in nanodisks , 2001 .

[5]  Matthew R. Gibbons,et al.  Magnetic domain structure and magnetization reversal in submicron-scale Co dots , 1998 .

[6]  Josef Zweck,et al.  Lorentz microscopy of circular ferromagnetic permalloy nanodisks , 2000 .

[7]  C. J. Cerjan,et al.  Nucleation and annihilation of magnetic vortices in submicron-scale Co dots , 2000 .

[8]  R. Cowburn,et al.  Single-Domain Circular Nanomagnets , 1999 .

[9]  J. Osborn.  Demagnetizing Factors of the General Ellipsoid , 1945 .

[10]  Evolution and stability of a magnetic vortex in a small cylindrical ferromagnetic particle under applied field , 2000, cond-mat/0012299.

[11]  E. Wohlfarth,et al.  A mechanism of magnetic hysteresis in heterogeneous alloys , 1948, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[12]  G. Bayreuther,et al.  Stability of magnetic tunnel junctions , 2002 .

[13]  G. Bayreuther,et al.  Magnetization reversal of sub-micron ferromagnetic tunnel junctions in external magnetic fields , 2002 .

[14]  H. Hoffmann,et al.  Magnetic switching of single vortex permalloy elements , 2001 .

[15]  J. Nowak,et al.  Spin vortex states and hysteretic properties of submicron size NiFe elements , 2000 .

[16]  G. A. Prinz,et al.  Switching of vertical giant magnetoresistance devices by current through the device , 1999 .

[17]  Joachim Wecker,et al.  Field programmable spin-logic based on magnetic tunnelling elements , 2002 .

[18]  William J. Gallagher,et al.  Exchange-biased magnetic tunnel junctions and application to nonvolatile magnetic random access memory (invited) , 1999 .

[19]  Ono,et al.  Magnetic vortex core observation in circular dots of permalloy , 2000, Science.

[20]  Saied N. Tehrani,et al.  High density submicron magnetoresistive random access memory (invited) , 1999 .

[21]  Paolo Vavassori,et al.  Magneto-optic Kerr effect investigation of cobalt and permalloy nanoscale dot arrays: Shape effects on magnetization reversal , 2000 .

[22]  J. N. Chapman,et al.  REVIEW ARTICLE: The investigation of magnetic domain structures in thin foils by electron microscopy , 1984 .