Anisotropic terahertz transmission induced by the external magnetic field in La0.67Ca0.33MnO3 film.

Hongying Mei,Shile Zhang,Feng Chen,Haizi Yao,Fuhai Su,Ruxian Yao,Peng Zhang,Zhenyou Wang

doi:10.1063/4.0000123

Abstract

A systemic investigation of the terahertz (THz) transmission of La0.67Ca0.33MnO3 film on the (001)-oriented NdGaO3 substrate under external magnetic field and low temperature have been performed. The significant THz absorption difference between the out-of-plane and the in-plane magnetic field direction is observed, which is consistent with the electrical transport measurement using the standard four-probe technique. Furthermore, we find that the complex THz conductivities can be reproduced in terms of the Drude Smith equation as the magnetic field is perpendicular to the film plane, whereas it deviates from this model when the in-plane magnetic field is applied. We suggest that such anisotropies in THz transport dynamics have close correspondences with the phase separation and anisotropic magnetoresistance effects in the perovskite-structured manganites. Our work demonstrates that the THz time-domain spectroscopy (TDS) can be an effective non-contact method for studying the magneto-transport properties of the perovskite-structured manganites.

Highlights

The physical properties of the perovskite-structured manganites at the low temperature and high external magnetic field condition have attracted intensive attention due to their interesting crystal structures and strong interplays among charge, lattice, spin, and orbital degrees of freedom
We find that the complex THz conductivities can be reproduced in terms of the Drude Smith equation as the magnetic field is perpendicular to the film plane, whereas it deviates from this model when the in-plane magnetic field is applied
We find that the THz transmission strongly depends on the magnetic field direction with respect to the film plane, which are consistent with the direct electrical transport measurement using the standard four-probe technique in the Physical Property Measurement System (PPMS, Quantum Design)

Summary

Introduction

The physical properties of the perovskite-structured manganites at the low temperature and high external magnetic field condition have attracted intensive attention due to their interesting crystal structures and strong interplays among charge, lattice, spin, and orbital degrees of freedom. This kind of material system exhibits plenty of novel physics phenomena, including the colossal magnetoresistance (CMR) effect, anisotropic magneto-resistance (AMR), metal– insulator transition (MIT), and phase separation (PS).. The PS is characterized by the competition between the ferromagnetic metallic (FMM) phase and the antiferromagnetic insulating (AFI) phase in perovskite-structured manganites. The transition, ranging from the AFI-dominant PS to the FMM-dominant PS in manganites, named the melting transition under the high magnetic field condition, which were usually explored with microscopy techniques. this electrical method is not applicable for the phase at nanometer scale due to the extremely strict measurement condition of the larger melting magnetic field for manganites. the electrical transport resistivity measurements can characterize the PS and AMR, it is inconvenient

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Conclusion