arXiv subjects

Alexander N. Taldenkov

Publications and source records attributed to Alexander N. Taldenkov.

7 recordsLinked to original sources

arXiv2026

Polymorph Engineering of the Layered Rare-Earth Magnet GdAlGe

The recent advances in research on layered magnets have established them as invaluable materials for spintronic applications and precursors to 2D magnets. The problem is that the number of such materials available for experimentation is still low. To tackle the problem, one may employ phase engineering; in particular, the interplay between the phase stability and dimensionality provides great opportunities for design of layered magnets. Here, this interrelation is harnessed to produce epitaxial films of an overlooked layered polymorph of GdAlGe. The compound is formed by alternating triangular Gd and honeycomb AlGe lattices. It is stable in ultrathin films, up to 5 monolayers. In thicker films, an additional unwanted phase emerges. The structural quality of the ultrathin films is witnessed by electron and X-ray diffraction as well as electron microscopy. Magnetization measurements detect an anisotropic ferromagnetic state. The GdAlGe magnetism is corroborated by a study of electron transport revealing the anomalous Hall effect and negative magnetoresistance. The material is naturally integrated with Ge, a technological semiconductor, which should facilitate applications. The present study can serve as a blueprint for design of layered magnets via polymorph engineering.

cond-mat.mtrl-sci↗

arXiv2026

Two-Dimensional Ferromagnetism in Monolayers of MnSi

2D ferromagnets offer valuable insights into the fundamentals of magnetism and stimulate the progress of ultracompact spintronics. The demand for seamless integration of the materials with the Si technology, particularly helpful to their applications in nanoelectronics, draws attention to 2D magnetic silicides. MnSi is a prominent silicide hosting magnetic phases with unconventional properties; however, little is known about magnetic states of MnSi at the 2D limit. Here, we explore the magnetism of ultrathin films of MnSi on silicon, down to a single monolayer. Angle-resolved photoemission spectra suggest exchange splitting of MnSi bands. Magnetization measurements confirm that the ferromagnetic state in MnSi is rather robust with respect to the number of monolayers. Thick metallic films demonstrate the anomalous Hall effect and negative magnetoresistance; however, as the number of monolayers drops below 3, MnSi becomes an insulator. Most importantly, the ferromagnetism of ultrathin MnSi films acquires a 2D character, as its effective Curie temperature depends on weak magnetic fields. The present study establishes MnSi monolayers as 2D ferromagnets that can find potential applications in silicon-based spintronics.

cond-mat.mtrl-sci↗

arXiv2025

Epitaxial graphene integrated with a monolayer magnet

Imprinting magnetism into graphene makes an important step to its applications in spintronics. An actively explored approach is proximity coupling of graphene to a 2D magnet. In these endeavors, the use of epitaxial graphene may bring significant advantages due to its superiority over the exfoliated counterpart and natural integration with the substrate but the problem of attaining magnetism persists. Here, we report synthesis and analysis of a heterostructure coupling epitaxial graphene with a regular lattice of magnetic atoms formed by Eu intercalation. The magnetization measurements reveal easy-plane 2D magnetism in the material, with the transition temperature controlled by low magnetic fields. The emerging negative magnetoresistance and anomalous Hall effect point at spin polarization of the carriers in graphene. In the paramagnetic phase, the magnetoresistance in graphene exhibits critical exponential behavior of the induced magnetic state. The intercalation does not compromise the parental electronic structure - quantum oscillations in the resistivity manifest low-mass carriers in graphene. The results are set against those for an isostructural material based on intercalated nonmagnetic Sr. Overall, the study expands the family of 2D magnets and establishes a prospective material for graphene-based spintronics.

cond-mat.mes-hall↗

arXiv2025

Competing Magnetic States in the Candidate Altermagnet GdAlGe

Altermagnetism, a newly discovered magnetic order, combines zero net magnetization with non-relativistic spin splitting of electronic bands. Its ability to utilize the advantages of both antiferromagnets and ferromagnets is highly promising for spintronic applications. Currently, the merge of altermagnetism and weak ferromagnetism in a single material excites significant interest as it provides additional control mechanisms over material properties. However, the role of dimensionality in this interplay is yet to be explored. Here, we study magnetism and electron transport in epitaxial films of the candidate altermagnet GdAlGe ranging from bulklike to a single monolayer. The films exhibit the anomalous Hall effect and negative magnetoresistance. In contrast to altermagnetic GdAlSi, the candidate altermagnet GdAlGe demonstrates an admixture of the ferromagnetic state which contribution increases as the system approaches the 2D limit. The coexistence of the magnetic states induces technologically important intrinsic exchange bias. The present work underpins future studies and applications of nanoscale altermagnets.

cond-mat.mtrl-sci↗

arXiv2025

Pushing an Altermagnet to the Ultimate 2D Limit: Evidence of Symmetry Breaking in Monolayers of GdAlSi

Altermagnets have emerged as a class of materials combining certain ferromagnetic properties with zero net magnetization. This combination is highly promising for spintronics, especially if a material can be brought to a nanoscale size. However, experimental studies of the 2D limit of altermagnets and evolution of their properties with thickness are lacking. Here, we study epitaxial films on silicon of the Weyl altermagnet GdAlSi ranging from more than a hundred unit cells to a single unit cell. The films are synthesized by molecular beam epitaxy and, expectedly, do not show any discernible net magnetic moments. Electron transport studies reveal a remarkable transformation of the electron state with the film thickness. Thick films exhibit negative longitudinal magnetoresistance associated with the chiral anomaly but do not demonstrate altermagnetic properties in electron transport due to symmetry restrictions. In ultrathin films, a spontaneous anomalous Hall effect manifests itself, indicating a non-relativistic spin splitting in the electronic structure. The transformation is associated with crystal symmetry breaking accompanying the 3D-to-2D crossover. The work highlights the role of dimensionality in altermagnetism and provides a platform for studies of altermagnets aiming at ultra-compact spintronics.

cond-mat.mtrl-sci↗

arXiv2024

Monolayer Magnetic Metal with Scalable Conductivity

2D magnets have emerged as a class of materials highly promising for studies of quantum phenomena and applications in ultra-compact spintronics. Current research aims at design of 2D magnets with particular functional properties. A formidable challenge is to produce metallic monolayers: the material landscape of layered magnetic systems is strongly dominated by insulators; rare metallic magnets, such as Fe3GeTe2, become insulating as they approach the monolayer limit. Here, electron transport measurements demonstrate that the recently discovered 2D magnet GdAlSi - graphene-like AlSi layers coupled to layers of Gd atoms - remains metallic down to a single monolayer. Band structure analysis indicates the material to be an electride, which may stabilize the metallic state. Remarkably, the sheet conductance of 2D GdAlSi is proportional to the number of monolayers - a manifestation of scalable conductivity. The GdAlSi layers are epitaxially integrated with silicon, facilitating applications in electronics.

cond-mat.mtrl-sci↗

arXiv2024

Engineering of a Layered Ferromagnet via Graphitization: An Overlooked Polymorph of GdAlSi

Layered magnets are stand-out materials because of their range of functional properties that can be controlled by external stimuli. Regretfully, the class of such compounds is rather narrow, prompting the search for new members. Graphitization - stabilization of layered graphitic structures in the 2D limit - is being discussed for cubic materials. We suggest the phenomenon to extend beyond cubic structures; it can be employed as a viable route to a variety of layered materials. Here, the idea of graphitization is put into practice to produce a new layered magnet, GdAlSi. The honeycomb material, based on graphene-like layers AlSi, is studied both experimentally and theoretically. Epitaxial films of GdAlSi are synthesized on silicon; the critical thickness for the stability of the layered polymorph is around 20 monolayers. Notably, the layered polymorph of GdAlSi demonstrates ferromagnetism stemming from the open 4f-shells of Gd, in contrast to the non-layered, tetragonal polymorph. The ferromagnetism is further supported by electron transport measurements revealing negative magnetoresistance and the anomalous Hall effect. The results show that graphitization can be a powerful tool in the design of functional layered materials.

cond-mat.mtrl-sci↗