Spin reorientation transitions in Pt/Co/Pt films under low dose Ga+ ion irradiation

Abstract

An elegant route for tuning the magnetic anisotropy of ultrathin Co films by Ga+ ion irradiation is presented. The magnetic anisotropy of a Pt/Co(2.6 nm)/Pt film is first changed from in-plane to out-of-plane by uniform low dose Ga+ ion irradiation at 30 keV. When increasing the dose, a second spin reorientation transition toward the sample plane is also evidenced. This could be a way to design magnetic nanowires with perpendicular anisotropy, embedded in an in-plane magnetized environment, either by irradiation through a mask or focused ion beam. Tentative explanations on the origin of these two successive spin reorientations are proposed.

The effect of a Pt impurity layer on the magnetocrystalline anisotropy of hexagonal close-packed Co: a first-principles study

“…The effects on the magnetic properties of CoPt as functions of the platinum content have been studied extensively, both theoretically [3] and experimentally [4,5]. Moreover, in recent experimental work [6] it was demonstrated that the magnetocrystalline anisotropy energy (MAE) of cobalt can be tuned by letting platinum impurities migrate into the cobalt system. Generally it is agreed that the addition of platinum to a magnetic material, such as Fe or Co, influences the magnetic properties, in particular, the MAE of the material primarily through the strong spin-orbit coupling of Pt [7].…”

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

“…In the quasi-uniform mode, the FIB is rapidly scanned over all the investigated film area. Some preliminary results were reported for sputtered Co (d Co = 1.4 nm) [13,29] and Co (d Co = 2.6 nm) [16] films. We evidenced rather similar magnetic changes by both irradiation procedures at comparable estimated fluences while the incoming Ga + ion rate in a nanosize region is much higher for the FIB procedure than for uniform irradiation.…”

“…As previously reported [13], the as-grown Pt/Co(1.4 nm)/Pt sputtered film (d Co < d SRT ), exhibits a square magnetic hysteresis loop at room temperature consistent with a rather large anisotropy field H ef f A = 1.9 kOe. On the contrary, for thicker Co layers (d Co > d SRT ) with in-plane anisotropy, d Co = 2.6 nm [16] or d Co = 3.0 nm (Fig. 2a), a pure S-shape field induced magnetization curve without hysteresis and with high saturation field was measured.…”

“…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].…”

“…Most of works were done on samples deposited by MBE technique. The influence of Ga ions beam bombardment on magnetic properties of sputtered Pt/Co/Pt was studied only in limited F range [16], i.e. only the branch 1 existence was reported.…”