In the realm of modern spintronics and magnonics, the efficient processing of information is often facilitated by laser-generated surface acoustic waves (SAWs). The ability to tune the parameters of these SAWs is crucial for achieving acoustic control over magnonic properties, which are essential for the development of next-generation data storage and processing devices. A recent study has shed light on a promising material that could revolutionize this field: the FeRh alloy.
FeRh is a unique metallic antiferromagnet at room temperature, known for its phase transition into a ferromagnetic state accompanied by a crystal lattice expansion at 370 K. This transition can also be induced by femtosecond laser pulses, making it an ideal candidate for studying the generation and control of SAWs. In their research, a team of scientists led by Ia. A. Mogunov and A. Yu. Klokov utilized a 60 nm Fe49Rh51 film to optically generate pulses of Gigahertz quasi-Rayleigh SAWs. These waves were detected via the photoelastic effect, revealing fascinating insights into the underlying mechanisms.
The study demonstrated that the lattice transformation during the phase transition is the dominant strain-generation mechanism for above-threshold excitation. As the sample is heated closer to the antiferromagnetic-ferromagnetic (AFM-FM) transition temperature, the contribution of this mechanism becomes more significant. However, when the sample is heated above the transition temperature, this contribution effectively “switches off,” allowing for precise control over the SAW amplitude. This tunability is a critical advancement for the field of spintronics and magnonics, as it enables researchers to manipulate magnonic properties with unprecedented accuracy.
The researchers also developed a model based on the thermodynamical parameters of Fe49Rh51, which showed that the lattice transformation occurring within 95 picoseconds effectively contributes to SAW generation happening on a comparable timescale. This finding underscores the importance of understanding the fast kinetics of phase transitions in magnetic materials for the development of advanced acoustic and spintronic devices.
The implications of this research are far-reaching, as the ability to control SAWs in phase-changing magnetic materials like FeRh could lead to significant advancements in information processing technologies. By harnessing the unique properties of these materials, scientists may be able to develop more efficient and powerful devices for data storage, communication, and computation. As the field of spintronics and magnonics continues to evolve, the insights gained from this study will undoubtedly play a pivotal role in shaping its future.
