The Origin of Weak Ferromagnetism in CaB6

M. C. Bennett; J. van Lierop; E. M. Berkeley; J. F. Mansfield; C. Henderson; M. C. Aronson; D. P. Young; A. Bianchi; Z. Fisk; F. Balakirev; A. Lacerda

arXiv · cond-mat/0306709

The Origin of Weak Ferromagnetism in CaB6

M. C. Bennett·J. van Lierop·E. M. Berkeley·J. F. Mansfield·C. Henderson·M. C. Aronson·D. P. Young·A. Bianchi·Z. Fisk·F. Balakirev·A. Lacerda

View original source ↗Read source document ↗Export metadata ↓

Abstract

We have combined the results of magnetization and Hall effect measurements to conclude that the ferromagnetic moments of lightly doped CaB6 samples display no systematic variation with electron doping level. Removal of the surface with acid etching substantially reduces the measured moment, although the Hall constant and resistivity are unaffected, indicating that the ferromagnetism largely resides on and near the sample surface. Electron microprobe experiments reveal that Fe and Ni are found at the edges of facets and growth steps, and on other surface features introduced during growth. Our results indicate that the weak ferromagnetism previously reported in undoped CaB6 is at least partly extrinsic.

Explore related subjects

cond-mat.str-el

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

M. C. Bennett, J. van Lierop, E. M. Berkeley, J. F. Mansfield, C. Henderson, M. C. Aronson, D. P. Young, A. Bianchi, Z. Fisk, F. Balakirev, A. Lacerda. 2003-06-29. The Origin of Weak Ferromagnetism in CaB6. https://arxiv.org/abs/cond-mat/0306709

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

KEEP EXPLORING

Related papers

arXiv2026

Observable-Based Learning of Effective Entanglement Hamiltonians

Determining the entanglement Hamiltonian (EH) of an interacting quantum many-body system remains a fundamental challenge beyond special analytically tractable cases. Here we develop an observable-matching framework for learning effective EHs, which we demonstrate using response estimates from quantum Monte Carlo. As applications of this framework, we first calibrate the overall prefactor of the lattice Bisognano--Wichmann (LBW) construction using equal-time correlations and then learn spatially resolved couplings beyond its prescribed profile, without assuming a specific functional form for their spatial dependence. Trained solely on local correlations, the learned EHs reproduce benchmarked von Neumann and second Rényi entropies in $1$D and second Rényi entropies in $2$D. For a strong-bond cut associated with special surface criticality at the $(2+1)$D $O(3)$ Wilson--Fisher critical point, free-form learning outperforms the calibrated LBW ansatz in predicting the second Rényi entropy and reveals spatially nonuniform coupling renormalizations. Importantly, the learned EH also provides access to the von Neumann entropy in this setting, revealing a negative subleading correction and extending previous Rényi entropy findings to the von Neumann case. Directly evaluating the von Neumann entropy in such $(2+1)$D interacting quantum many-body systems remains challenging for conventional numerical methods. These results establish observable-based learning as a route to constructing effective entanglement Hamiltonians beyond prescribed spatial profiles in higher-dimensional interacting systems.

cond-mat.str-el↗

arXiv2026

Extensions of the Haldane gap proof: higher dimensions, near degeneracy, fermions and tensor-network states

A recent remarkable paper by OpenAI showed that the spin-one Heisenberg chain with periodic boundary conditions has a spectral gap in the thermodynamic limit. The proof elegantly deduces this gap from the Hamiltonian's spectrum on a finite system. This basic idea is an inequality involving the purity of the original Gibbs state and a dual Gibbs state that is defined via space-time rotation. Here we consider a few generalizations of this purity bootstrap argument. We first extend it to arbitrary spatial dimensions. Our main result uses the space-time duality between symmetry generators and symmetry twists to obtain upper bounds on the splitting of nearly degenerate low-energy states, together with a nonzero gap above them, from finite-system information. As applications, we show that finite-system calculations for the 2+1-D toric code in a field and the 2+1-D transverse-field Ising model establish parameter regimes with four and two low-lying states whose splittings are bounded from above by $e^{-cL}$ and $e^{-cL^2}$ respectively for arbitrarily large system size $L$, while the gap above these states remains nonzero in the thermodynamic limit. Next, we extend it to fermionic systems and use a finite calculation to establish a symmetric mass generation phase in a $2+1$-D fermionic model. Finally, we apply the bootstrap to tensor-network states and establish exponential decay of connected correlations of all local operators in the symmetric square-lattice spin-one state introduced by Jian and Zaletel.

cond-mat.str-el↗

arXiv2026

Interfacial polarity control of anomalous Hall effect in LaCoO3-SrIrO3 heterostructures

Interfacial polarity in oxide heterostructures can drive robust charge redistribution across the interface, yet its role in tailoring topological transport phenomena like the anomalous Hall effect (AHE) remains largely unexplored. Here, we control the sign of polarity-induced charge in SrIrO3-LaCoO3 interfaces by independently engineering the layer stacking sequence and the atomic termination. In-situ angle-resolved photoemission spectroscopy directly confirms the sign reversal of the induced charge in SrIrO3 through the contrasting electronic band shifts between different interfacial configurations. Magneto-transport measurements across a systematic matrix of four distinct heterostructures reveal that the AHE can be cleanly toggled on and off: it emerges exclusively under electron-doped conditions, while remaining suppressed for hole-doped SrIrO3. Our results establish that this response originates from an intrinsic, Berry-curvature-driven mechanism governed by polarity-controlled band filling of SrIrO3. These findings shift interfacial polarity from a passive structural consequence to an active design variable for engineering topological quantum states in oxide heterostructures.

cond-mat.str-el↗