Itinerant ferromagnetism in rocksalt NdO epitaxial thin films

Rocksalt NdO (001) epitaxial thin films were synthesized. Contrary to paramagnetic NdO bulk polycrystal in previous studies, NdO epitaxial thin films showed ferromagnetism with a Curie temperature of 19.1 ± 1.8 K, originating from dominant direct Nd−Nd exchange interaction owing to the small intercationic distance. In addition, negative magnetoresistance and an anomalous Hall effect were observed.

Figure 1

Magnetic transition temperatures of NdPns and NdChs. Blue and red shaded areas correspond to ferromagnetic and antiferromagnetic phases, respectively. Inset shows the rocksalt structure of NdXs.

Figure 2

(a) X-ray diffraction $\theta -2\theta$ pattern and (b) reciprocal space map at around 224 diffraction for NdO (001) epitaxial thin film on $\mathrm{YAl}{\mathrm{O}}_3$ (110) substrate.

Figure 3

(a) Temperature dependence of magnetization for NdO epitaxial thin film at 0.05 T (FC: red; ZFC: blue). Inset shows temperature dependence of inverse susceptibility. (b) Magnetic field dependence of magnetization at different temperatures from 2 to 100 K. Magnetic field was applied to the out-of-plane [001] direction in these measurements.

Figure 4

(a) Temperature dependence of resistivity for NdO epitaxial thin film at various magnetic fields. Inset shows overall view of 2–300 K. (b) Magnetic field dependence of anomalous Hall conductivity at different temperatures from 2 to 50 K. The magnetic field was applied to the out-of-plane [001] direction.