Angular dependence of the photothermally modulated magnetic resonance in Gd thin films

In this paper we use electron spin resonance and photothermally modulated magnetic resonance techniques to investigate gadolinium thin films as a function of the orientation of the film surface with respect to the external magnetic field and of the temperature, around the magnetic phase transition temperature. We observe that, in the ferromagnetic phase, the resonance line is shifted up to higher external magnetic fields when the angle between the film surface and the field increases, revealing the magnetic anisotropy of the sample. At the same time, when the temperature is augmented to values higher than the phase transition temperature, the external field of the resonance collapses back to the expected value in the paramagnetic phase for all orientations. We also demonstrated that, even for the perpendicular orientation (magnetic field perpendicular to the sample surface), the photothermally modulated magnetic resonance signal is maximized near the magnetic phase transition temperature. Furthermore, in the ferromagnetic phase the photothermally modulated magnetic resonance intensity is very sensitive to the orientation, showing a significant enhancement in the perpendicular direction.