Eur. Phys. J. B (2013) 86: 52
https://doi.org/10.1140/epjb/e2012-30566-3

Regular Article

Tuning optical and ferromagnetic properties of thin GdN films by nitrogen-vacancy centers^*

¹ Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, 657-8501 Kobe, Japan
² Center for Support to Research and Education Activities, Kobe University, 1-1 Rokkodai, 657-8501 Kobe, Japan
³ Molecular Photoscience Research Center and Graduate School of Science, Kobe University, 1-1 Rokkodai, 657-8501 Kobe, Japan

^a e-mail: drsagar@sapphire.kobe-u.ac.jp

Received: 9 July 2012
Received in final form: 22 August 2012
Published online: 13 February 2013

Abstract

AlN/GdN/AlN double heterostructures were grown on c-sapphire substrates using a reactive rf sputtering method under high vacuum conditions. The optical absorption spectrum of the GdN shows a clear fundamental band edge of GdN around 800 nm; this transition is attributed to the minority spin band energy of GdN at the X point. Nitrogen vacancy centers cause a blue-shift of the optical band edge of GdN, which could be ascribed to both the band filling, and the electron-hole interactions resulting from the free carriers generated by nitrogen vacancies. Temperature-dependent magnetization measurements demonstrate a clear change in the magnetization values of GdN with respect to the N₂ partial pressure. Nitrogen vacancy centers in the thin GdN film raise the Curie temperature from 31 K to 39 K, which has been accurately measured by the Arrott plots.