### Abstract

We developed a method to engineer the surface topography of Nb underlayers using surface oxidation followed by low energy Ar ion milling to improve the properties of subsequently deposited magnetic Ni<formula><tex>$_{80}$</tex></formula>Fe<formula><tex>$_{20}$</tex></formula> (Permalloy) thin films. The reduced coercivity H<formula><tex>$_{c}$</tex></formula>, increased remanent squareness, and improved magnetic anisotropy in Ni<formula><tex>$_{80}$</tex></formula>Fe<formula><tex>$_{20}$</tex></formula> thin films deposited on oxidized and subsequently ion milled Nb was found to be primarily due to the reduced roughness of the Nb underlayer, especially at high spatial frequency (> 25 μm<formula><tex>$^{-1}$</tex></formula>). The typical results that we obtained for Ni<formula><tex>$_{80}$</tex></formula>Fe<formula><tex>$_{20}$</tex></formula> films 2.4 nm thick deposited on Nb 100 nm thick was an easy axis coercivity H<formula><tex>$_{ce}$</tex></formula> = 3.7 Oe (6 Oe without smoothing), a hard-axis H<formula><tex>$_{ch}$</tex></formula> = 1.5 Oe (5.5 Oe without smoothing), an easy axis remanent squareness Sq<formula><tex>$_{e}$</tex></formula> = M<formula><tex>$_{r}$</tex></formula>/M<formula><tex>$_{s}$</tex></formula> = 0.92, a hard-axis remanent squareness Sq<formula><tex>$_{h}$</tex></formula>= 0.25, and a uniaxial anisotropy H<formula><tex>$_{k}$</tex></formula> of = 6.0 Oe, all measured at T = 10 K. This ion-smoothing technique could potentially be used to improve the properties of magnetic layers in superconducting memory and other magnetoelectronic devices which utilize a thick underlayer that serves as an electrical contact.

Original language | English (US) |
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Journal | IEEE Magnetics Letters |

DOIs | |

Publication status | Accepted/In press - Nov 18 2017 |

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### Keywords

- Magnetic films
- Magnetic measurements
- Soft Magnetic Materials

### ASJC Scopus subject areas

- Electronic, Optical and Magnetic Materials

### Cite this

*IEEE Magnetics Letters*. https://doi.org/10.1109/LMAG.2017.2776079