Phys.org March 28, 2024
Most macroscopic magnetic phenomena (including magnetic hysteresis) are typically understood classically. An international team of researchers (USA – Caltech, University of Colorado, University of Chicago, University of Tennessee, Canada, Japan, UK) examined the dynamics of a uniaxial rare-earth ferromagnet deep within the quantum regime, so that domain wall motion, and the associated hysteresis, was initiated by quantum nucleation, which then grew into large-scale domain wall motion, that was observable as an unusual form of Barkhausen noise. They found that the “quantum Barkhausen noise” exhibited two distinct mechanisms for domain wall movement, each of which was quantum-mechanical, but with very different dependences on an external magnetic field applied transverse to the spin (Ising) axis. These observations were understood in terms of the correlated motion of pairs of domain walls, nucleated by cotunneling of plaquettes (sections of domain wall), with plaquette pairs correlated by dipolar interactions; this correlation was suppressed by the transverse field. According to the researchers similar macroscopic correlations may be expected to appear in the hysteresis of other systems with long-range interactions… read more. 1 TECHNICAL ARTICLE
2 Open Access TECHNICAL ARTICLE
Low-frequency SdH oscillations… Credit: PNAS, February 5, 2024, 121 (7) e2315787121