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Hariom Jani1 3 Jiajun Linghu5 Rajesh Chopdekar4 Sonu Devi1 Yonghua Du6 Changjian Li8 Ping Yang6 Sreetosh Goswami1 3 Soumya Sarkar1 3 Siddhartha Ghosh1 Elke Arenholz4 Mike Coey7 Yuan Ping Feng5 Thirumalai Venkatesan1 3 2

1, NanoCore, Singapore, , Singapore
3, NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, Singapore, Singapore
5, Physics, National University of Singapore, Singapore, , Singapore
4, Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States
6, Singapore Synchroton Light Source, National University of Singapore, Singapore, , Singapore
8, MSE, National University of Singapore, Singapore, , Singapore
7, CRANN, Trinity College, Dublin, , Ireland
2, ECE, National University of Singapore, Singapore, Singapore, Singapore

α-Fe2O3 hosts in-plane Antiferromagnetism (AFM) at room temperature, possessing spin canting due to the Dzyaloshinskii-Moriya interaction. Just 100C below zero, bulk α-Fe2O3 undergoes Morin transition where the AFM spins re-orient colinearly along the out-of-plane symmetry axis. This first-order transition emerges due to the competition between magnetic-dipolar and single-ion magnetic anisotropies which have different magnitudes and temperature dependences.

We have a developed a catalytic process for doping hydrogen into the α-Fe2O3 lattice, which allows non-volatile tuning of the AFM Néel vector and the accompanying spin canting. We discover that hydrogen doping also increases the electronic conductivity of α-Fe2O3 by three orders of magnitude. Moreover, owing to the light mass of a hydrogen atom, our H-doping process can be performed post-growth and is also reversible.

We characterize the new α-Fe2O3Hx phase via Reciprocal Space Mapping, Raman and UV-Vis Spectroscopy, Scanning Tunnelling Electron Microscopy and X-Ray Magnetic Linear Dichroism. We use Elastic Recoil Detection Analysis to prove that hydrogenation indeed causes incorporation of H atoms in the α-Fe2O3 lattice. X-Ray Absorption Near Edge Structure and ab-initio calculations reveal that the hydrogenation induced magnetic and electric modulations in α-Fe2O3 are concomitant with electron doping and not due to any structural changes of the lattice. This Electronic doping plays a crucial role in tuning the relative magnitude of the single-ion anisotropy with respect to the magnetic-dipolar counter-part, causing the modulation of the Morin transition. Our approach opens new avenues for control of anti-ferromagnetism in oxide systems.

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