# Large Uniaxial Anisotropy Induced in Soft Ferromagnetic Thin Films by Oblique Deposition of Underlayer

Rakesh Singh, Nicholas D. Rizzo, Ashwin Boochakravarthy, Nathan Newman

Research output: Contribution to journalArticle

3 Citations (Scopus)

### Abstract

We produced a large uniaxial anisotropy (H<formula><tex>$_{\rm k}$</tex></formula>) in ultra-thin (1.2 to 2.4 nm) soft ferromagnetic layers through the oblique deposition of a nm-thick metallic underlayer. Fe, Ni and Ni<formula><tex>$_80$</tex></formula>Fe<formula><tex>$_20$</tex></formula> (Permalloy) films deposited on a 5 nm thick Nb layer grown at an oblique angle (up to 60&#x00B0;) exhibit a H<formula><tex>$_{\rm k}\approx$</tex></formula>40-500 Oe and have properties that are nearly ideal for use as a fixed layer in magnetic devices such as for magnetic memory. A much higher induced H<formula><tex>$_{\rm k}$</tex></formula> is observed in Ni (500 Oe) and Fe (300 Oe) compared to NiFe (40 Oe). We used this technique to increase H<formula><tex>$_sw$</tex></formula> by 3X-5X in an array of pattered Fe or NiFe bits, and achieved an excellent relative switching distribution of <formula><tex>$\approx$</tex></formula>0.05-0.06. We also controllably enhanced the H<formula><tex>$_{\rm k}$</tex></formula> in the fixed layer of patterned spin-valve devices for superconducting memory (JMRAM) and produced a large difference in H<formula><tex>$_{\rm sw}$</tex></formula> between the fixed and free layers. Different spacer layers between the Nb and the magnetic layers were found to either transmit (Ru) or reduce (Cu, Ru/Al, ion-milled Ru) the effect of the oblique Nb. This technique was also effectively used in synthetic antiferromagnet (SAF) structures, and therefore has the potential to eliminate the need for an antiferromagnetic-pinning layer when it degrades magnetic device performance.

Original language English (US) IEEE Magnetics Letters https://doi.org/10.1109/LMAG.2017.2779101 Accepted/In press - Nov 29 2017

### Fingerprint

Magnetic devices
Anisotropy
Data storage equipment
Thin films
Ions

### Keywords

• Iron
• Magnetic anisotropy
• Magnetic films
• Magnetic Films
• Magnetic Measurements
• Nickel
• Niobium
• Soft Magnetic Materials
• Superconducting magnets

### ASJC Scopus subject areas

• Electronic, Optical and Magnetic Materials

### Cite this

Large Uniaxial Anisotropy Induced in Soft Ferromagnetic Thin Films by Oblique Deposition of Underlayer. / Singh, Rakesh; Rizzo, Nicholas D.; Boochakravarthy, Ashwin; Newman, Nathan.

In: IEEE Magnetics Letters, 29.11.2017.

Research output: Contribution to journalArticle

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AB - We produced a large uniaxial anisotropy (H$_{\rm k}$) in ultra-thin (1.2 to 2.4 nm) soft ferromagnetic layers through the oblique deposition of a nm-thick metallic underlayer. Fe, Ni and Ni$_80$Fe$_20$ (Permalloy) films deposited on a 5 nm thick Nb layer grown at an oblique angle (up to 60°) exhibit a H$_{\rm k}\approx$40-500 Oe and have properties that are nearly ideal for use as a fixed layer in magnetic devices such as for magnetic memory. A much higher induced H$_{\rm k}$ is observed in Ni (500 Oe) and Fe (300 Oe) compared to NiFe (40 Oe). We used this technique to increase H$_sw$ by 3X-5X in an array of pattered Fe or NiFe bits, and achieved an excellent relative switching distribution of $\approx$0.05-0.06. We also controllably enhanced the H$_{\rm k}$ in the fixed layer of patterned spin-valve devices for superconducting memory (JMRAM) and produced a large difference in H$_{\rm sw}$ between the fixed and free layers. Different spacer layers between the Nb and the magnetic layers were found to either transmit (Ru) or reduce (Cu, Ru/Al, ion-milled Ru) the effect of the oblique Nb. This technique was also effectively used in synthetic antiferromagnet (SAF) structures, and therefore has the potential to eliminate the need for an antiferromagnetic-pinning layer when it degrades magnetic device performance.

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