Structural and magnetic properties of biaxially textured NiFe2O4 thin films grown on c-plane sapphire

Abstract

Chemical solution deposition is used to grow biaxially textured NiFe2O4 (NFO) thin films on (0001) sapphire substrates; a high degree of out-of-plane orientation in the 〈111〉 direction is confirmed by θ–2θ X-ray diffraction and pole figures. X-ray φ-scanning indicates in-plane texture and an epitaxial relationship between NFO (111) and Al2O3 (0001) in two crystallographic variants. The out-of-plane magnetization exhibits improved Mr/Ms from 0.5 in 110 nm-thick films to 0.8 in 60 nm-thick films. Compared to uniaxially textured NFO films on platinized silicon, the out-of-plane coercivity is reduced by 20%. The improved out-of-plane magnetic anisotropy is comparable to epitaxial NFO films of similar thickness deposited by pulsed laser deposition and sputtering.

Optimized Growth of Heteroepitaxial (111) NiFe2O4 Thin Films on (0001) Sapphire with Two In‐Plane Variants via Chemical Solution Deposition

“…The NFO films show a six‐fold symmetry along the <111> axis with 30° rotation with respect to the sapphire peaks. Similar to our previous results the average full width at half maximum (FWHM) of the NFO peaks is estimated as 1.5°, which is consistent with a relatively good epitaxial match between the (111) NFO and the (0001) sapphire . Figure depicts the top‐view HIM image of the epitaxial (111) NFO thin film.…”

“…Figure depicts the top‐view HIM image of the epitaxial (111) NFO thin film. The (111) NFO and (0001) sapphire are epitaxially related in two in‐plane variants of [110] NFO ∥ or , which are rotated by 60° with respect to each other. Nucleation of small grains, mostly at the kinks, indicates the surface diffusion of atoms to the kink sites, which are energetically more favorable for nucleation.…”

“…Most recently, we reported on uniaxially and biaxially textured NFO thin films deposited on (111) Pt and (0001) sapphire substrates, respectively . The textured films grown here by CSD are deposited and annealed at much lower temperature than previously reported epitaxial/textured NFO films by other techniques .…”

“…The 0.5 and 0.2 Molar (M) NFO precursor solutions are synthesized following a route based on 2‐methoxyethanol (CH 3 OCH 2 CH 2 OH) as solvent, described in detail previously . Nickel acetate tetrahydrate (Ni(CO 2 CH 3 ) 2 ·4H 2 O) and ferric nitrate nonahydrate (Fe(NO 3 ) 3 ·9H 2 O) are used as precursors (all supplied from Sigma Aldrich, Inc., St. Louis, MO).…”

“…Most recently, we reported on uniaxially and biaxially textured NFO thin films deposited on (111) Pt and (0001) sapphire substrates, respectively. 17,18 The textured films grown here by CSD are deposited and annealed at much lower temperature than previously reported epitaxial/textured NFO films by other techniques. 4,6,7 Here, we vary the processing parameters of biaxially textured NFO on c-plane sapphire to improve the degree of texture, achieve the epitaxial NFO thin films, and better understand the epitaxial relationship between the NFO films and sapphire substrates.…”