Modifications of magnetic properties of Pt/Co/Pt thin layers by focused gallium ion beam irradiation

We show how the magnetic properties of the Pt/Co ultrathin film structure can be modified and even controlled under uniform irradiation by Ga+ ions at low fluence in the 20–100 keV range. A systematic magneto-optical study is presented for the Pt/Co(1.4 nm)/Pt(111) ultrathin-film structure. At ion fluences below D=1014 Ga+/cm2, the coercive field is steadily reduced when increasing the fluence. At large fluences, in the range D=(5–10)×1014 Ga+ ions/cm2, the magnetization of the Co layer drops rapidly and the film finally becomes paramagnetic at room temperature for D>2×1015 Ga+ ions/cm2. We demonstrate that these magnetic changes are related to the effect of ion-induced collisional intermixing of the Co/Pt interfaces, leading to the formation of stable Co–Pt alloys with varying composition across the interfaces. A simple model is derived to relate the ion beam-induced mixing to the changes in magnetic properties. The present work allows us to gain a quantitative understanding of previous experiments using...

[1]  J. Biersack,et al.  Calculation of projected ranges — analytical solutions and a simple general algorithm , 1981 .

[2]  W. Johnson,et al.  When is thermodynamics relevant to ion-induced atomic rearrangements in metals? , 1985 .

[3]  J. Giérak,et al.  Observation and simulation of focused ion beam induced damage , 1994 .

[4]  C. Leroux,et al.  LETTER TO THE EDITOR: Magnetic properties and chemical ordering in Co-Pt , 1988 .

[5]  Imaging of magnetic domains in thin Co/Pt and CoNi/Pt multilayers by near-field magneto-optical circular dichroism , 1998 .

[6]  Claude Chappert,et al.  Nanoscale Magnetic Domains in Mesoscopic Magnets , 1996, Science.

[7]  Peter Vettiger,et al.  Patterning magnetic films by ion beam irradiation , 2000 .

[8]  Paul B. Fischer,et al.  Single‐domain magnetic pillar array of 35 nm diameter and 65 Gbits/in.2 density for ultrahigh density quantum magnetic storage , 1994 .

[9]  William J. Gallagher,et al.  Magnetization Reversal in Micron-Sized Magnetic Thin Films , 1998 .

[10]  J. Ferré,et al.  Magneto‐optical anisometry of ultrathin cobalt films , 1993 .

[11]  T. Devolder,et al.  SUB-50 NM PLANAR MAGNETIC NANOSTRUCTURES FABRICATED BY ION IRRADIATION , 1999 .

[12]  Claude Chappert,et al.  Magnetic anisotropy in metallic ultrathin films and related experiments on cobalt films (invited) , 1988 .

[13]  T. Devolder.  Light ion irradiation of Co/Pt systems: Structural origin of the decrease in magnetic anisotropy , 2000 .

[14]  C. Chappert,et al.  DOMAIN WALL CREEP IN AN ISING ULTRATHIN MAGNETIC FILM , 1998 .

[15]  T. Devolder,et al.  Planar patterned magnetic media obtained by ion irradiation , 1998, Science.

[16]  Christophe Vieu,et al.  Optimization of experimental operating parameters for very high resolution focused ion beam applications , 1997 .

[17]  V. Mathet,et al.  Magnetization Reversal in Arrays of Perpendicularly Magnetized Ultrathin Dots Coupled by Dipolar Interaction , 1998 .

[18]  S. Chou,et al.  Fabrication of single‐domain magnetic pillar array of 35 nm diameter and 65 Gbits/in.2 density , 1994 .

[19]  Margaret Evans Best,et al.  Ion induced magnetization reorientation in Co/Pt multilayers for patterned media , 2000 .

[20]  S. Parkin,et al.  Epitaxial growth of Pt on basal-plane sapphire: a seed film for artificially layered magnetic metal structures , 1993 .

[21]  M. Sutton,et al.  MeV ion irradiation of Co/Cu multilayers , 1997 .

[22]  A. Traverse,et al.  Quantitative Description of Mixing with Light Ions , 1989 .

[23]  A. Viegas,et al.  Structural and magnetic behavior of ar+-implanted co/pd multilayers : interfacial mixing , 1994 .

[24]  T. D. Harris,et al.  Breaking the Diffraction Barrier: Optical Microscopy on a Nanometric Scale , 1991, Science.

[25]  Claude Chappert,et al.  DYNAMICS OF THE MAGNETIZATION REVERSAL IN AU/CO/AU MICROMETER-SIZE DOT ARRAYS , 1998 .

[26]  C. Chappert,et al.  Irradiation induced effects on magnetic properties of Pt/Co/Pt ultrathin films , 1999 .

[27]  Very thin Fe/Ni modulation multilayer films under ion bombardment , 1997 .

[28]  L. Néel.  Anisotropie magnétique superficielle et surstructures d'orientation , 1954 .

[29]  C. Chien,et al.  Effects of Ar-ion implantation and annealing on structural and magnetic properties of Co/Pd multilayers , 1994 .

[30]  Bruce D. Terris,et al.  Near‐field optical data storage using a solid immersion lens , 1994 .

[31]  T. Devolder,et al.  ION BEAM INDUCED MAGNETIC NANOSTRUCTURE PATTERNING , 1999 .