Epitaxial growth and magnetic properties of NixFe4-xN (x = 0, 1, 3, and 4) films on SrTiO3(001) substrates

Abstract

The 20-60 nm-thick epitaxial Ni x Fe 4-x N (x ¼ 0, 1, 3, and 4) films were successfully fabricated on SrTiO 3 (001) single-crystal substrates by alternating the substrate temperature (T sub), and their crystalline qualities and magnetic properties were investigated. It was found that the crystal orientation and the degree of order of N site were improved with the increase of T sub for x ¼ 1 and 3. The lattice constant and saturation magnetization decreased as the Ni content increased. This tendency was in good agreement with first-principle calculation. Curie temperature of the Ni 3 FeN film was estimated to be 266 K from the temperature dependence of magnetization. The Ni 4 N film was not ferromagnetic but paramagnetic due to its low degree of order of N site. Published by AIP Publishing.

Negative anisotropic magnetoresistance resulting from minority spin transport in NixFe4−xN (x = 1 and 3) epitaxial films

“…These magnetotransport properties are similar to those in Fe 4 N and Co 3 FeN. [10][11][12][13][14][15] The temperature dependence of r AMR of Ni 21 We therefore may state that larger jr AMR j for Ni 3 electrons along the current direction. According to the AMR theory taking the crystal field effect and SOI into account, the magnitude of s-d scattering is modified depending on the D (d) split by the crystal field effect.…”

“…The T c of Ni 3 FeN was determined to be about 260 K from the temperature dependence of magnetization. 21 This might be the reason why r AMR is close to 0 at 250 K or higher in Figs. 5(a) and 5(b).…”

“…From r AMR < 0 shown in Figs. 4 and 5, and aforementioned theory stating P D < 0, 21 the relation of ðr " À r # Þ < 0 is obtained from Eq. (1).…”

“…13,23 Calculation details are described in our previous paper. 21 We assumed that Ni and Fe atoms were randomly distributed in the lattice. The resistivity of the films was measured from 8 to 300 K by van der Pauw method using a closed-cycle He cryostat.…”

“…21 Previously, we successfully grew Ni x Fe 4Àx N (x ¼ 0, 1, 3, and 4) films by molecular beam epitaxy (MBE) and investigated their magnetic properties. 21 The Curie temperature (T c ) of Ni 3 FeN was found to be lower than 300 K. According to Loloee, however, Ni 3 FeN epitaxial films grown on an Al 2 O 3 (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) substrate exhibited a large positive r AMR reaching 6% at room temperature (RT). 22 This result means that the T c of Ni 3 FeN was above RT in contrast to our result.…”