We grew Mn4N epitaxial thin films capped with Au layers on MgO(001) and SrTiO3(001) substrates by molecular beam epitaxy. Perpendicular magnetic anisotropy (PMA) was confirmed in all the samples at room temperature from the magnetization versus magnetic field curves using superconducting quantum interference device magnetometer. From the ω-2θ x-ray diffraction (XRD) and ϕ-2θχ XRD patterns, the ratios of perpendicular lattice constant c to in-plane lattice constant a, c/a, were found to be about 0.99 for all the samples. These results imply that PMA is attributed to the in-plane tensile strain in the Mn4N films.

Line oscillator strengths in the 20 electric dipole-allowed bands of (14)N(2) in the 89.7-93.5 nm (111480-106950 cm(-1)) region are reported from photoabsorption measurements at an instrumental resolution of approximately 6 mA (0.7 cm(-1)) full width at half maximum. The absorption spectrum comprises transitions to vibrational levels of the 3p sigma(u) c(4)' (1)Sigma(u)(+), 3p pi(u) c(3) (1)Pi(u), and 3s sigma(g) o(3) (1)Pi(u) Rydberg states and of the b' (1)Sigma(u)(+) and b (1)Pi(u) valence states. The J dependences of band f values derived from the experimental line f values are reported as polynomials in J'(J'+1) and are extrapolated to J'=0 in order to facilitate comparisons with results of coupled Schrodinger-equation calculations. Most bands in this study are characterized by a strong J dependence of the band f values and display anomalous P-, Q-, and R-branch intensity patterns. Predissociation line widths, which are reported for 11 bands, also exhibit strong J dependences. The f value and line width patterns can inform current efforts to develop comprehensive spectroscopic models that incorporate rotational effects and predissociation mechanisms, and they are critical for the construction of realistic atmospheric radiative-transfer models.

15We have attempted to grow single-crystalline Co 4 N thin films on SrTiO 3 (STO) (001) 16substrates by molecular beam epitaxy by the simultaneous supply of 3N-Co and

10-nm-thick γ′-Fe4N films were grown epitaxially on LaAlO3(001) and MgO(001) substrates by molecular beam epitaxy using solid Fe and a radio-frequency NH3 plasma. The lattice mismatch of these substrates to γ′-Fe4N is 0% and 11%, respectively. Spin and orbital magnetic moments of these γ′-Fe4N epitaxial films were deduced by x-ray magnetic circular dichroism measurements at 300 K. The total magnetic moments are almost the same for the two substrates, that is, 2.44±0.06 μB and 2.47±0.06 μB, respectively. These values are very close to those predicted theoretically, and distinctively larger than that for α-Fe.

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