arXiv subjects

Marcus Ekholm

Publications and source records attributed to Marcus Ekholm.

7 recordsLinked to original sources

arXiv2026

Altermagnetism of ultrathin CrSb slabs

Altermagnets exhibit momentum-dependent spin splitting without net magnetization, combining characteristics of both ferromagnets and antiferromagnets, making them highly interesting for spintronics applications. CrSb is a prime candidate with a high Néel temperature ($\sim700$~K) and a large exchange-driven splitting of $\sim0.6$--1~eV. Using ab-initio calculations, we consider slabs of various orientations in the ultrathin limit. We find that (100) oriented slabs have spin-degenerate bands. In (0001) oriented slabs, the exchange-driven altermagnetic spin splitting collapses, but including spin-orbit coupling restores a residual anisotropic splitting of $\sim70$~meV. In contrast, the (110) oriented slabs show an altermagnetic spin splitting of $\sim400$~meV, and emerges as a robust candidate for realizing large, exchange-driven altermagnetism

cond-mat.str-el↗

arXiv2025

Magnetic, Structural, and Electronic Properties of CrOCl with the PBE Functional

CrOCl is a van der Waals-layered insulator with an antiferromagnetic ground state, making it a promising platform for exfoliation and the exploration of low-dimensional magnetism. An accurate ab initio description is therefore essential. Previous density-functional studies have shown that DFT+$U$ calculations may erroneously favor ferromagnetic order depending on the choice of parametrization, an issue that cannot be remedied by simply adjusting the value of $U$. Here, we demonstrate that an explicit Hubbard correction is unnecessary: the PBE functional correctly reproduces the AFM ground state while simultaneously improving the description of structural properties. Moreover, PBE provides a reliable account of the electronic structure. These findings clarify the role of correlation effects in CrOCl and identify PBE as a robust starting point for future ab initio studies of CrOCl-based materials.

cond-mat.mtrl-sci↗

arXiv2023

Lattice Distortions and Magnetic Interactions in Single-Layer VOCl

Atomically thin layers exfoliated from magnetic van der Waals layered materials are currently of high interest in solid state physics. VOCl is a quasi-two-dimensional layered antiferromagnet which was recently synthesized in monolayer form. Previous theoretical studies have assumed the high-temperature orthorhombic lattice symmetry also in the low temperature range, where the bulk system is known to be monoclinic due to a strong magnetoelastic coupling. We demonstrate from \textit{ab-initio} calulations that this monoclinic distortion is prevalent also in monolayers, which is in line with recent experimental indications of monoclinic symmetry. Our calculations also show that competing ferromagnetic and antiferromagnetic interactions give rise a frustrated two-fold magnetic superstructure where higher-order magnetic interactions play a key role to stabilize the observed magnetic ground state.

cond-mat.mtrl-sci↗

arXiv2019

Mott and spin-Peierls physics in TiPO$_4$ under high pressure

TiPO$_4$ is a Mott insulator and one of few inorganic compounds featuring a spin-Peierls phase at low temperature. Recent experimental studies have suggested the presence of spin-Peierls dimerization also at ambient temperature though at high pressure. Here, we present a combined experimental and theoretical study of the energetics of the high-pressure phase. We analyse dimerization properties and their coupling to spin degrees of freedom. Most importantly, we argue that TiPO$_4$ resents a direct analogue to the celebrated binary transition metal oxide VO$_2$. TiPO$_4$ allows to assess spin-dimer physics in the high-pressure regime in a controlled fashion, having the potential to become an important model system representative of the class of dimerized transition metal oxides.

cond-mat.str-el↗

arXiv2019

Inverse pressure-induced Mott transition in TiPO$_4$

TiPO$_4$ shows interesting structural and magnetic properties as temperature and pressure are varied, such as a spin-Peierls phase transition and the development of incommensurate modulations of the lattice. Recently, high pressure experiments for TiPO$_4$ reported two new structural phases appearing at high pressures, the so-called phases IV and V [M. Bykov et al., Angew. Chem. Int. Ed. 55, 15053]. The latter was shown to include the first example of 5-fold O-coordinated P-atoms in an inorganic phosphate compound. In this work we characterize the electronic structure and other physical properties of these new phases by means of ab-initio calculations, and investigate the structural transition. We find that the appearance of phases IV and V coincides with a collapse of the Mott insulating gap and quenching of magnetism in phase III as pressure is applied. Remarkably, our calculations show that in the high pressure phase V, these features reappear, leading to an antiferromagnetic Mott insulating phase, with robust local moments.

cond-mat.str-el↗

arXiv2019

The role of magnetic order in VOCl

VOCl and other transition metal oxychlorides are candidate materials for next-generation rechargeable batteries. We have investigated the influence of the underlying magnetic order on the crystallographic and electronic structure by means of density functional theory. Our study shows that antiferromagnetic ordering explains the observed low-temperature monoclinic distortion of the lattice, which leads to a decreased distance between antiferromagnetically coupled V-V nearest neighbors. We also show that the existence of a local magnetic moment removes the previously suggested degeneracy of the occupied levels, in agreement with experiments. To describe the electronic structure, it turns out crucial to take the correct magnetic ordering into account, especially at elevated temperature.

cond-mat.mtrl-sci↗

arXiv2015

Pressure induced crossing of the core-levels in 5d metals

Pressure induced interaction between core electrons, the core level crossing (CLC) transition has been observed in hcp Os at P~400 GPa [L. Dubrovinksy, et al., Nature 525, 226-229 (2015)]. In this work, we carry out a systematic study of the influence of pressure on the electronic structure in all metals of the 5d series (Hf,Ta,W,Re,Os,Ir,Pt,Au) using first-principles electronic structure calculations. We have found that CLC is a general effect for this series of metals. While in Pt it occurs at ~1500 GPa, at a pressure substantially higher than in Os, in Ir it occurs already at 80 GPa. Moreover, we predict that in Re the CLC transition may appear at ambient pressure. We analyze the shifts of the CLC transition pressure across the series within the Thomas-Fermi model, and show that the effect has many common features to the atomic collapse in the rare-earth elements.

cond-mat.mtrl-sci↗