arXiv subjects

Srdjan Stavrić

Publications and source records attributed to Srdjan Stavrić.

9 recordsLinked to original sources

arXiv2026

Orbital mixing and strong Hund's coupling stabilize spin order in van der Waals ferromagnet CrI3

Recent years have seen a vast increase in research into van der Waals magnetic materials. In many of these systems, magnetism is introduced via light 3d-transition metal elements, combined with chalcogenides or halogens. Despite the high technological promise in the field of spintronics, the connection between the d-orbital configuration and the occurrence of low-dimensional magnetic order is currently unclear. Here we address the prototypical two-dimensional ferromagnet CrI3, via complementary spectroscopies and density functional theory calculations. We reveal the electronic structure and orbital character of bulk CrI3 in the paramagnetic and ferromagnetic phases, describing the couplings underpinning its energy diagram, and providing a robust experimental demonstration that the stabilization of ferromagnetism is attributable to orbital mixing between I p and Cr eg states, and to the presence of strong Hund's coupling. These findings reveal the microscopic connection between orbital and spin degrees of freedom, providing fundamental insights into the behavior of low-dimensional magnetic materials.

cond-mat.mtrl-sci↗

arXiv2025

AMaRaNTA: Automated First-Principles Exchange Parameters In 2D Magnets

Two-dimensional (2D) magnets host a wide range of exotic magnetic textures, whose low-energy excitations and finite-temperature properties are typically described by effective spin models based on Heisenberg-like Hamiltonians. A key challenge in this framework is the reliable determination, from ab initio calculations, of exchange parameters and their anisotropic components, crucial for stabilising long-range order. Among the different strategies proposed for this task, the energy-mapping method -- based on total-energy calculations within Density Functional Theory (DFT) -- is the most widely adopted, but it typically requires laborious, multi-step procedures. To overcome this limitation, we introduce AMaRaNTA (Automating Magnetic paRAmeters iN a Tensorial Approach), a computational package that systematically automates the energy-mapping method, specifically through its ``four-state'' formulation, to extract exchange and anisotropy parameters in 2D magnets. In its current implementation, AMaRaNTA returns the nearest-neighbour exchange tensor, complemented by scalar parameters for second- and third-nearest-neighbour exchange interactions as well as single-ion anisotropy. Together, these provide a minimal yet sufficient set of parameters to capture magnetic frustration and anisotropies, essential for stabilising several observed magnetic states in 2D materials. Applied to a representative subset of the Materials Cloud 2D Structure database, AMaRaNTA demonstrates robust, automated and reproducible screening of magnetic interactions, with clear potential for high-throughput simulations.

cond-mat.mtrl-sci↗

arXiv2025

Hole doping as an efficient route to increase the Curie temperature in monolayer CrI$_3$

Two-dimensional van der Waals (vdW) magnets offer unprecedented opportunities to control magnetism at the atomic scale. Through charge carrier doping - realized by electrostatic gating, intercalation/adsorption, or interfacial charge transfer - one can efficiently tune exchange interactions and spin-orbit-induced effects in these systems. In this work, through a multi-scale theoretical framework combining density functional theory, spin Hamiltonian modeling, and Wannier-function analysis, we choose monolayer CrI$_3$ to unravel how carrier doping affects the isotropic as well as anisotropic exchange interactions in this prototypical vdW ferromagnet. The remarkable efficiency of hole doping in enhancing ferromagnetic exchange and magnetic anisotropy found in our study was explained through orbital-resolved analysis. Crucially, we demonstrated that unlike the undoped system - where isotropic exchange interactions govern magnetic long-range order - the hole-doped CrI$_3$ exhibits anisotropic terms comparable in magnitude to isotropic ones. Finally, we show that a high concentration of holes in a CrI$_3$ monolayer can increase its Curie temperature above 200 K. This work advances our understanding of doping-controlled magnetism in semiconducting 2D materials, demonstrating how anisotropy engineering can stabilize high-temperature magnetic order.

cond-mat.mtrl-sci↗

arXiv2025

Electrical switching of an unconventional odd parity magnet

Magnetic states with zero magnetization but non-relativistic spin splitting are outstanding candidates for the next generation of spintronic devices. Their electron-volt (eV) scale spin splitting, ultrafast spin dynamics and nearly vanishing stray fields make them particularly promising for several applications. A variety of such magnetic states with nontrivial spin textures have been identified recently, including even-parity d, g, or i-wave altermagnets and odd-parity p-wave magnets. Achieving voltage-based control of the nonuniform spin polarization of these magnetic states is of great interest for realizing energyefficient and compact devices for information storage and processing. Spin-spiral type-II multiferroics are optimal candidates for such voltage-based control, as they exhibit an inversion-symmetry-breaking magnetic order which directly induces ferroelectric polarization, allowing for symmetry protected cross-control between spin chirality and polar order. Here we combine photocurrent measurements, first-principle calculations and group-theory analysis to provide direct evidence that the spin polarization of the spin-spiral type-II multiferroic NiI2 exhibits odd-parity character connected to the spiral chirality. The symmetry-protected coupling between chirality and polar order enables electrical control of a primarily non-relativistic spin polarization. Our findings represent the first direct observation of unconventional odd-parity magnetism in a spin-spiral type-II multiferroic, and open a new frontier of voltage-based switching of non-relativistic spin polarization in compensated magnets.

cond-mat.mes-hall↗

arXiv2025

Giant non-reciprocal band structure effect in a multiferroic material

Multiferroic materials, characterized by the coexistence of ferroelectricity and ferromagnetism, may unveil band structures suggestive of complex phenomena and new functionalities. In this Letter, we analyze the band structure of EuO in its multiferroic phase. Using density functional theory calculations and detailed symmetry analysis, we reveal a previously overlooked non-reciprocal band structure effect, where the electronic energy bands exhibit asymmetry along opposite directions with respect to the special points in the Brillouin zone. This effect, which is enabled by spin-orbit coupling, is giant for the top valence Eu $4f$ bands, and can be switched by external electric or magnetic fields. Furthermore, this results in an enhanced bulk photovoltaic effect. Specifically, our predictions indicate the emergence of a large injection current response to linearly polarized light, resulting in a photoconductivity value several orders of magnitude higher than that reported in any other oxide material. Ultimately, this non-reciprocal band structure effect and the associated large bulk photovoltaic response may be general phenomena emerging not just in EuO but also in other multiferroics or magnetoelectrics, potentially providing new cross-functionalities.

cond-mat.mtrl-sci↗

arXiv2024

Avoided metallicity in a hole-doped Mott insulator on a triangular lattice

Doping of a Mott insulator gives rise to a wide variety of exotic emergent states, from high-temperature superconductivity to charge, spin, and orbital orders. The physics underpinning their evolution is, however, poorly understood. A major challenge is the chemical complexity associated with traditional routes to doping. Here, we study the Mott insulating CrO$_2$ layer of the delafossite PdCrO$_2$, where an intrinsic polar catastrophe provides a clean route to doping of the surface. From scanning tunnelling microscopy and angle-resolved photoemission, we find that the surface stays insulating accompanied by a short-range ordered state. From density functional theory, we demonstrate how the formation of charge disproportionation results in an insulating ground state of the surface that is disparate from the hidden Mott insulator in the bulk. We demonstrate that voltage pulses induce local modifications to this state which relax over tens of minutes, pointing to a glassy nature of the charge order.

cond-mat.str-el↗

arXiv2024

Interplay of altermagnetism and weak ferromagnetism in two-dimensional RuF$_4$

Gaining growing attention in spintronics is a class of magnets displaying zero net magnetization and spin-split electronic bands called altermagnets. Here, by combining density functional theory and symmetry analysis, we show that RuF$_4$ monolayer is a two-dimensional $d$-wave altermagnet. Spin-orbit coupling leads to pronounced spin splitting of the electronic bands at the $Γ$ point by $\sim 100$ meV and turns the RuF$_4$ into a weak ferromagnet due to non trivial spin-momentum locking that cants the Ru magnetic moments. The net magnetic moment scales linearly with the spin-orbit coupling strength. Using group theory we derive an effective spin Hamiltonian capturing the spin-splitting and spin-momentum locking of the electronic bands. Disentanglement of the altermagnetic and spin-orbit coupling induced spin splitting uncovers to which extent the altermagnetic properties are affected by the spin-orbit coupling. Our results move the spotlight to the non trivial spin-momentum locking and weak ferromagnetism in the two-dimensional altermagnets relevant for novel venues in this emerging field of material science research.

cond-mat.mtrl-sci↗

arXiv2023

Delving into the anisotropic interlayer exchange in bilayer CrI$_3$

Bilayer CrI$_3$ attracted much attention owing to peculiar switching between the layered ferromagnetic and antiferromagnetic order upon stacking alternation. This finding pointed out the importance of the apparently small interlayer exchange, yet, existing literature addresses only its isotropic part. To fill this gap, we combine the density functional theory with Hamiltonian modeling to examine the anisotropic interlayer exchange in bilayer CrI$_3$ - Dzyaloshinskii-Moriya (DMI) and the Kitaev interaction (KI). We develop and apply a novel computational procedure that yields the off-diagonal exchange matrix elements with $μ$eV accuracy. Inspecting two types of bilayer stacking, we found a weak interlayer KI and much stronger DMI between the sublattices of monoclinic bilayer and their complete absence in rhombohedral bilayer. We show how these anisotropic interactions depend on the interlayer distance, stacking sequence, and the spin-orbit coupling strength and suggest the dominant superexchange processes at play. In addition, we demonstrate that the single-ion anisotropy largely depends on stacking, increasing by 50% from monoclinic to rhombohedral structure. Remarkably, our findings prove that iodines, owing to their spatially extended 5p orbitals featuring strong spin-orbit coupling, are extremely efficient in mediating DMI across the van der Waals gap in two-dimensional magnetic heterostructures. Given that similar findings were previously demonstrated only in metallic multilayers where the DMI shows a much longer range, our study gives promise that the chiral control of spin textures can be achieved in two-dimensional semiconducting magnetic bilayers whose ligands feature strong spin-orbit coupling.

cond-mat.mtrl-sci↗

arXiv2017

Adsorption Sites of Individual Metal Atoms on Ultrathin MgO(100) Films

We use Ca doping during growth of one and two monolayer thick MgO films on Ag(100) to identify the adsorption sites of individual adatoms with scanning tunneling microscopy. For this we combine atomic resolution images of the bare MgO layer with images of the adsorbates and the substitutional Ca atoms taken at larger tip-sample distance. For Ho atoms, the adsorption sites depend on MgO thickness. On the monolayer, they are distributed on the O and bridge sites according to the abundance of those sites, 1/3 and 2/3 respectively. On the MgO bilayer, Ho atoms populate almost exclusively the O site. A third species adsorbed on Mg is predicted by density functional theory and can be created by atomic manipulation. Au atoms adsorb on the bridge sites for both MgO thicknesses, while Co and Fe atoms prefer the O sites, again for both thickness.

cond-mat.mtrl-sci↗