Enhancement of spin wave group velocity in ferrimagnets with angular momentum compensation

Abstract

In this study, we theoretically investigated properties of magnetostatic spin waves in rare-earth and transition-metal ferrimagnets with various angular momentum. The resonant frequency of high- (low-) frequency mode has the lowest (highest) value at angular momentum compensation temperature (TA). It was found that both resonance modes show a maximum group velocity at TA. Furthermore, the low-frequency mode shows higher group velocity than the high-frequency mode at any temperature. Our findings are the key to advance both the physics and the technology to develop research field of magnonics based on the antiferromagnetic spin waves.