Omnipolar Magnetic Field Detection by Superlattice‐Based Hall Sensor

ABSTRACT Magnetic‐field–induced electronic switching has been investigated in (La 0 . 7 Sr 0 . 3 MnO 3 ) m –(BiFeO 3 ) n (LSMO‐BFO) superlattices engineered with unit‐cell precision to probe interfacial spin–charge coupling in complex oxide heterostructures. Pulsed laser deposition with RHEED‐controlled growth enabled the realization of coherently strained superlattices exhibiting atomically controlled layering and well‐defined periodicity. Systematic variation of LSMO and BFO layer thicknesses reveals that ferromagnetism is strongly suppressed in ultrathin LSMO, yet interfacial spin‐canted regions persist above the LSMO Curie temperature, enabling anomalous Hall transport dominated by interface‐driven correlations. Superlattices grown on TiO 2 ‐ vs. SrO‐terminated SrTiO 3 substrates exhibit distinct interfacial sequences and roughness, leading to measurable differences in magnetization, Curie temperature, and electronic conduction. Remarkably, Hall resistance measurements uncovered an abrupt, hysteretic switching between high‐and low‐resistance states at temperatures significantly above the LSMO Curie temperature. This switching is polarity‐independent with respect to magnetic‐field direction, demonstrating omnipolar anomalous Hall switching originating from magnetization reversals within interfacial Fe─Mn exchange‐coupled layers. The effect is absent in the longitudinal magnetoresistance, confirming its Hall‐specific origin. These findings establish LSMO–BFO superlattices as a robust platform for omnipolar magnetic‐field sensing and highlight the critical role of atomic‐layer interface engineering in controlling emergent spin–orbit–coupled transport phenomena in correlated oxide heterostructures.