Perpendicular magnetic anisotropy in a Pt/Co/Pt ultrathin film arising from a lattice distortion induced by ion irradiation

Modification of Magnetic Properties of Pt/Co/Pt Films by Ga+ Ion Irradiation: Focused versus Uniform Irradiation

“…Recent spectroscopic magneto-optical investigations [18] revealed a negative PKR peak at 3.2 eV in a comparable weakly irradiated (in branch 1) Pt/Co(2.6 nm)/Pt sputtered film (with F = 10 14 Ga + ions/cm 2 ) that can be the signature of an hcp Co 0.75 Pt 0.25 ordered alloy phase with high magnetic anisotropy, as already reported by several authors [51][52][53][54]. According to the simulation results [24] the amount of local chemical ordering phase is not significant but together with induced tensile in-plane strain [17,24] can explain the restored PMA in the "branch 1" region of the (d Co , F ) phase diagram [22].…”

“…Second, at moderate fluence (F = 4 × 10 14 to 5 × 10 15 Ga + ions/cm 2 ), there appears only isotropic Co lattice deformation [17]. Moreover, the PMA interface term is reduced under irradiation favoring intermixing at Pt/Co interfaces ( Fig.…”

“…in branch 1) under irradiation both in the sputtered or MBE grown Pt/Co(3 nm)/Pt films: (i) the irradiation-induced inplane lattice expansion [17,24], (ii) the irradiationinduced formation of high anisotropy species near disturbed Co/Pt interfaces. For the item (ii), structural changes are driven by collision cascades of ions that generate thermal spikes inside which the temperature rises up to several thousand kelvins, i.e.…”

“…Since few years, the influence of the uniform Ga + ions bombardment on properties of Pt/Co/Pt layers has been studied also for d Co > d SRT for nanostructures deposited by either sputtering [16][17][18] or molecular beam epitaxy (MBE) [19][20][21][22] techniques. Using a wide range of ions fluence F (up to ion-driven nanostructure erosion) we have found some new phenomena, such as: (i) existence of two regions with increased magnetic anisotropy, usually connected with increased out-of-plane remnant magnetization, named "branch 1 and 2" in the (d Co , F ) phase diagram [22]; (ii) enhanced magneto-optical effects [21,22].…”

“…X-ray absorption spectra (XAS), X-ray magnetic circular dichroism (XMCD), and extended X-ray absorption fine structure (EXAFS) techniques [17,20,22,23], as well as classical molecular dynamics and Monte Carlo simulations [24], were used for studies of Ga-ions-driven modification of Pt/Co/Pt structures. These changes in magnetic properties were interpreted by considering the competition between the interface and the bulk contributions, the last one being attributed to disordered or ordered CoPt alloys formation [22], lattice stresses [17,24] and Co-platelet formation [20]. Most of works were done on samples deposited by MBE technique.…”