Chapter 1
Chiral Coupling to Magnetodipolar
Radiation
Tao Yu and Gerrit E. W. Bauer
Abstract We review and extend the theory of chiral pumping of spin waves by
magnetodipolar stray fields that generate unidirectional spin currents and asymmetric magnon densities. We illustrate the physical principles by two kinds of chiral
excitations of magnetic films, i.e., by the evanescent Oersted field of a narrow metallic stripline with an AC current bias and a magnetic nanowire under ferromagnetic
resonance.
1.1 Introduction
“Handedness” or “chirality” of wave propagation is a lively research topic in optics,
acoustics, and condensed matter physics. The “spin” of magnons is rooted in the
time-reversal symmetry breaking of the magnetic order and leads to chiral coupling
with other excitations when locked to the momentum. This phenomenon is governed
by non-universal selection rules. This chapter clarifies a specific mechanism, viz.
evanescent microwaves that can efficiently generate chiral dynamics.
Magnonics and magnon spintronics [1–4] are emergent fields that hold the promise
of a next-generation low-power and scalable information processing and communication technology. The generation of coherent and propagating spin waves is a crucial
ingredient, which can be realized by magnetic fields generated by microwave antennas such as current-biased metallic striplines. In order to generate stray fields with
T. Yu (B)
Max Planck Institute for the Structure and Dynamics of Matter,
Luruper Chaussee 149, 22761 Hamburg, Germany
e-mail: tao.yu@mpsd.mpg.de
G. E. W. Bauer
Institute for Materials Research & WPI-AIMR & CSRN, Tohoku University,
Sendai 980-8577, Japan
e-mail: G.E.W.Bauer@tudelft.nl
Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft,
The Netherlands
© Springer Nature Switzerland AG 2021
E. Kamenetskii (ed.), Chirality, Magnetism and Magnetoelectricity,
Topics in Applied Physics 138,
https://doi.org/10.1007/978-3-030-62844-4_1
1
Chiral Coupling to Magnetodipolar
Radiation
Tao Yu and Gerrit E. W. Bauer
Abstract We review and extend the theory of chiral pumping of spin waves by
magnetodipolar stray fields that generate unidirectional spin currents and asymmetric magnon densities. We illustrate the physical principles by two kinds of chiral
excitations of magnetic films, i.e., by the evanescent Oersted field of a narrow metallic stripline with an AC current bias and a magnetic nanowire under ferromagnetic
resonance.
1.1 Introduction
“Handedness” or “chirality” of wave propagation is a lively research topic in optics,
acoustics, and condensed matter physics. The “spin” of magnons is rooted in the
time-reversal symmetry breaking of the magnetic order and leads to chiral coupling
with other excitations when locked to the momentum. This phenomenon is governed
by non-universal selection rules. This chapter clarifies a specific mechanism, viz.
evanescent microwaves that can efficiently generate chiral dynamics.
Magnonics and magnon spintronics [1–4] are emergent fields that hold the promise
of a next-generation low-power and scalable information processing and communication technology. The generation of coherent and propagating spin waves is a crucial
ingredient, which can be realized by magnetic fields generated by microwave antennas such as current-biased metallic striplines. In order to generate stray fields with
T. Yu (B)
Max Planck Institute for the Structure and Dynamics of Matter,
Luruper Chaussee 149, 22761 Hamburg, Germany
e-mail: tao.yu@mpsd.mpg.de
G. E. W. Bauer
Institute for Materials Research & WPI-AIMR & CSRN, Tohoku University,
Sendai 980-8577, Japan
e-mail: G.E.W.Bauer@tudelft.nl
Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft,
The Netherlands
© Springer Nature Switzerland AG 2021
E. Kamenetskii (ed.), Chirality, Magnetism and Magnetoelectricity,
Topics in Applied Physics 138,
https://doi.org/10.1007/978-3-030-62844-4_1
1