Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.23764

Temperature and Thickness Dependent Spin Current Transmission through Epitaxial Antiferromagnetic α-Fe2O3

Koushik Prabhakara·Rajeev Nepal·Subhashree Chatterjee·Rabindra Basnet·Ezana Negusse·Ramesh C Budhani
View original source ↗Read source document ↗Export metadata ↓

Abstract

Antiferromagnetic insulator α-Fe2O3 is a potential medium for coherent motion of spin waves over relatively large distances, allowing non-dissipative transfer of information between circuit elements. However, the structural defects and temperature dependent spin reorientations in this oxide impact the propagation. Understanding how the magnetic state of an antiferromagnetic insulator affects spin-current transmission is therefore important for elucidating the mechanisms governing spin transport. Here, we report spin-current transmission through epitaxial α-Fe2O3 thin films sandwiched between Permalloy and Pt. Using spin pumping and inverse spin Hall effect, we observe a finite symmetric dc voltage across the Pt layer over the temperature range 1.6 to 300 K for alpha-Fe2O3 thicknesses of 0, 30, 40, and 100 nm. The symmetric voltage coefficient Ks exhibits two approximately linear temperature regimes, separated by a characteristic temperature T* whose value depends on the thickness of the α-Fe2O3 layer. Further, the dc magnetization measurements on some of the samples suggest that the T* is correlated with the spin reorientation transition (Morin transition) in α-Fe2O3. Interestingly, a significantly larger magnitude of dKs/dT is noted below the characteristic temperature T*. The observed thickness and temperature dependent spin-current transmission indicates a sensitivity to the magnetic state of the insulating hematite layer.

Explore related subjects

cond-mat.mtrl-scicond-mat.mes-hall

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Koushik Prabhakara, Rajeev Nepal, Subhashree Chatterjee, Rabindra Basnet, Ezana Negusse, Ramesh C Budhani. 2026-10-16. Temperature and Thickness Dependent Spin Current Transmission through Epitaxial Antiferromagnetic α-Fe2O3. https://arxiv.org/abs/2610.23764

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Resolving the energy alignment between methylammonium lead iodide and C60: an in-situ photoelectron spectroscopy study

Understanding and controlling the energy level alignment at interfaces between lead halide perovskites and electron transport layers is crucial for optimizing perovskite-based devices such as solar cells. In this work, we investigated the energy level alignment of C60 on in-situ cleaved MAPbI3 single crystals in multiple repeat experiments using photoelectron spectroscopy aiming to resolve inconsistencies reported in earlier studies. Our results show that both materials remain chemically stable upon interface formation, in contrast to the strong reactions typically seen when metals are evaporated on perovskite surfaces. By analyzing the Pb 4f and C 1s binding energies in detail, we determined that C60 consistently exhibits a downward energy shift toward MAPbI3, which works against efficient charge extraction. The magnitude of this shift, however, varies between different sample positions, highlighting that small variations in sample surfaces can lead to significant differences in energetic alignment. These findings underscore the decisive role of surface chemistry on interfacial energetics, explain performance variability in perovskite devices, and demonstrate the need to control and accurately measure surface properties. Furthermore, the observed energetic alignment can explain why further interface modification by charge blocking layers or surface passivation is needed for optimized device efficiencies.

cond-mat.mtrl-sci↗
arXiv2026

Data-Efficient Indentation Size Effect Mitigation in Steels Using Machine Learning and a Physics-Constrained Neural Network

Shallow nanoindentation, needed for thin layers, individual phases and small volumes, gives hardness inflated by the indentation size effect (ISE). The Nix-Gao correction reduces this inflation but requires deep indentations of the same material, often impossible in such samples. We present a data-efficient workflow, trained on a few reference materials, that predicts a high-load reference hardness from a single shallow indentation. Seven models were trained on 703 indentations (5-350 mN) on three steels (2.0-6.5 GPa): Ridge regression, Random Forest, XGBoost, two feed-forward networks, and two physics-constrained neural networks (PCNNs) that apply a bounded learned correction q as H_app/sqrt(1+q). Over five seeds, models were tested on an external steel not used for training and indented at different loads, in leave-one-steel-out folds, and on fused silica, an out-of-domain material where all models failed. Random Forest and XGBoost, the best on the development set, transferred worst over all loads (MAPE 10.2 and 8.5%), whereas Ridge regression, the PCNNs and one feed-forward network reached 3.7-4.8%; with three training steels, development-set accuracy thus did not indicate accuracy on an unseen steel. From only the external steel's 3-15 mN indentations, the smooth (non-tree) models estimated the reference within 0.03-0.19 GPa on average. The PCNNs matched the linear baseline within the training hardness range and were the most accurate for a held-out steel softer than the training steels, but failed for a harder one. The workflow uses no steel-specific inputs and can be retrained for other material classes.

cond-mat.mtrl-sci↗
arXiv2026

Theoretical study of nitrogen-vacancy spin coherence enhanced by vacancy aggregation in diamond using cluster-correlation expansion

Annealing a semiconductor makes its vacancies mobile; they aggregate into multi-vacancy complexes that often carry spin. Such centres are a magnetic-noise source for any spin qubit among them, in silicon and silicon carbide as well as in diamond, and they are accordingly blamed for NV- decoherence in irradiated and implanted diamond, with two coherence records credited to removing them. Cluster-correlation-expansion simulations driven by published electron-paramagnetic-resonance parameters invert that attribution. At a fixed paramagnetic spin density a multi-vacancy bath gives a Hahn-echo coherence time 3.1-7.1 times longer than a bath of isolated negative vacancies, over three decades of concentration. A bath dephases the qubit because its spins exchange spin projections with one another, and two can exchange only if their transition frequencies match. A fine-structure splitting shifts those frequencies. Were every defect on the same crystallographic site, all would shift alike and still match: worth only a factor 1.15. Real defects occupy symmetry-equivalent sites pointing in different directions, so neighbours land at different frequencies and stop exchanging: a further 2.7. What governs the coherence time is therefore the fraction of bath pairs sharing a transition frequency, not the zero-field splitting. Vacancy aggregation extends NV- spin coherence rather than shortening it.

cond-mat.mtrl-sci↗