Journal article Open Access

Ion irradiation-induced easy-cone anisotropy in double-MgO free layers for perpendicular magnetic tunnel junctions

B. M. S. Teixeira; A. A. Timopheev; N. F. F. Caçoilo; S. Auffret; R. C. Sousa; B. Dieny; E. Alves; N. A. Sobolev


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{
  "publisher": "Zenodo", 
  "DOI": "10.5281/zenodo.3674060", 
  "language": "eng", 
  "title": "Ion irradiation-induced easy-cone anisotropy in double-MgO free layers for perpendicular magnetic tunnel junctions", 
  "issued": {
    "date-parts": [
      [
        2018, 
        5, 
        15
      ]
    ]
  }, 
  "abstract": "<p>We have used the ferromagnetic resonance in the X-band (9.37&thinsp;GHz) to investigate the effect of 400&thinsp;keV Ar<sup>+</sup> irradiation on the perpendicular magnetic anisotropy (PMA) and Gilbert damping parameter, &alpha;, of double-MgO free layers designed for application in perpendicular magnetic tunnel junctions. The samples comprised a MgO/Fe<sub>72</sub>Co<sub>8</sub>B<sub>20</sub>/X(0.2&thinsp;nm)/Fe<sub>72</sub>Co<sub>8</sub>B<sub>20</sub>/MgO layer stack, where X stands for an ultrathin Ta or W spacer. Samples with two different total FeCoB layer thicknesses, t<sub>FCB</sub>&thinsp;=&amp;thinsp;3.0&thinsp;nm and t<sub>FCB</sub>&thinsp;=&amp;thinsp;2.6&thinsp;nm, were irradiated with ion fluences ranging from 10<sup>12</sup>&thinsp;cm<sup>&minus;2</sup> to 10<sup>16</sup>&thinsp;cm<sup>&minus;2</sup>. The effective first-order PMA field, B<sub>K1</sub>, decreased nearly linearly with the logarithm of the fluence for both FeCoB thicknesses and spacer elements. The decrease in B<sub>K1</sub>, which is likely caused by an ion-induced intermixing at the FeCoB/MgO interfaces, resulted in a reorientation of the magnetization of the free layers with t<sub>FCB</sub>&thinsp;=&amp;thinsp;2.6&thinsp;nm, initially exhibiting a perpendicular easy-axis anisotropy. For intermediate fluences, 10<sup>13</sup>&thinsp;cm<sup>&minus;2</sup> and 10<sup>14</sup>&thinsp;cm<sup>&minus;2</sup>, easy-cone states with different cone angles could be induced in the free layer with a W spacer. Importantly, no corresponding increase in the Gilbert damping was observed. This study shows that ion irradiation can be used to tune the easy-cone anisotropy in perpendicular magnetic tunnel junctions, which is interesting for spintronic applications such as spin-torque magnetic memory devices, oscillators, and sensors.</p>", 
  "author": [
    {
      "family": "B. M. S. Teixeira"
    }, 
    {
      "family": "A. A. Timopheev"
    }, 
    {
      "family": "N. F. F. Ca\u00e7oilo"
    }, 
    {
      "family": "S. Auffret"
    }, 
    {
      "family": "R. C. Sousa"
    }, 
    {
      "family": "B. Dieny"
    }, 
    {
      "family": "E. Alves"
    }, 
    {
      "family": "N. A. Sobolev"
    }
  ], 
  "version": "Author Accepted Manuscript", 
  "type": "article-journal", 
  "id": "3674060"
}
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