Electric-field control of spin waves at room temperature in multiferroic BiFeO3

Abstract: To face the challenges lying beyond current CMOS-based technology, new paradigms for information processing are required. Magnonics proposes to use spin waves to carry and process information, in analogy with photonics that relies on light waves, with several advantageous features such as potential operation in the THz range and excellent coupling to spintronics. Several magnonic analog and digital logic devices have been proposed, and some demonstrated. Just as for spintronics, a key issue for magnonics is the large power required to control/write information (conventionally achieved through magnetic fields applied by strip lines, or by spin transfer from large spin-polarized currents). Here we show that in BiFeO3, a room-temperature magnetoelectric material, the spin wave frequency (>600 GHz) can be tuned electrically by over 30%, in a non-volatile way and with virtually no power dissipation. Theoretical calculations indicate that this effect originates from a linear magnetoelectric effect related to spin-orbit coupling induced by the applied electric field. We argue that these properties make BiFeO3 a promising medium for spin wave generation, conversion and control in future magnonics architectures.

• The paper shows non-volatile tuning of spin wave frequencies by over 30% using electric fields at room temperature.
• It employs Raman spectroscopy to track changes in cyclon and extra cyclon modes, ensuring precise frequency measurements.
• The findings reveal that the linear magnetoelectric effect coupled with spin-orbit interactions enables energy-efficient modulation for magnonic applications.

Electric-Field Control of Spin Waves in BiFeO₃ at Room Temperature

The paper explores the manipulation of spin wave frequencies through the application of electric fields in the multiferroic material BiFeO₃ (BFO). This investigation is motivated by the potential for developing new paradigms necessary for future information processing technologies that may exceed the capabilities of current CMOS-based approaches. The study leverages the multiferroic properties of BFO, mainly its coexistence of ferroelectric and magnetic orders, enabling the electrical control of spin wave dynamics with minimal power dissipation.

Spin waves—magnetic excitations useful for information processing—pose a unique opportunity for reducing energy consumption in data manipulation. Conventional control of spin information is typically achieved through magnetic fields generated by electrical currents, which are inherently energy-intensive. Here, the researchers demonstrate the ability to control spin wave dynamics electrically in BFO, potentially operating at frequencies exceeding 600 GHz, with shifts in spin wave frequency reaching over 30%, using negligible power.

Key Findings

• Spin Wave Control: The electrical manipulation of spin waves was realized at room temperature, enabling non-volatile spin wave frequency tuning by over 30%. The frequency adjustment is achieved through electrical fields that induce shifts in the spin wave oscillations of the cycloidal magnetic structure inherent to BFO.
• Experimental Techniques: The study employs Raman spectroscopy to observe spin wave modes within BFO. The application of an electric field results in distinct changes in the Raman spectra, indicating shifts in the frequency of different spin wave modes (labeled as cyclon and extra cyclon modes).
• Mechanisms: The researchers suggest that the linear magnetoelectric effect contributes significantly to the observed phenomena, postulating a coupling between the electric field and the spin-orbit interactions present in the material. Theoretical models using Landau free energy reveal that these effects manifest specifically as modulations in magnetic anistropy energies induced by the applied field, particularly in the presence of spin-orbit interactions.

Implications

The ability to control spin waves through electric fields opens avenues for novel magnonic devices that offer low-power operations compared to traditional electronic devices. BFO, as demonstrated, is a promising candidate for applications in magnonics due to its room-temperature multiferroic properties and significant frequency tuning range.

Future Directions

The exploration of BFO could lead to advances in spintronics and magnonics, especially in the field of device applications that require efficient information processing at high frequencies. Further research into the interactions at higher electric fields and the implications of magnetoelectric couplings could provide additional insights, enhancing the integration of multiferroic materials in technological applications. Additionally, exploring different multiferroic materials with varied coupling strengths and symmetries could also yield robust systems for future innovations beyond current CMOS capabilities.

In conclusion, the paper presents substantial evidence of the electrical manipulation of spin waves in BFO, a capability that is crucial for the development of next-generation technologies in spintronics and magnonics, marking an important advancement in the field of multiferroic materials research.