Quantum Altermagnetism Demonstrates New Ordering at Zero Temperature in Diffusive Systems

The behaviour of electrons in disordered metals presents a long-standing challenge in condensed matter physics, and recent work explores a novel magnetic state called altermagnetism. Alberto Cortijo from the Instituto de Ciencia de Materiales de Madrid (ICMM), along with colleagues, investigates the conditions under which this unusual magnetic order emerges in two-dimensional electron systems. Their research reveals that altermagnetism becomes favoured over conventional ferromagnetism as the strength of material anisotropy increases, and importantly, they demonstrate that this state persists even in the presence of external magnetic fields. This discovery expands our understanding of magnetic ordering in materials and could prove significant for the development of future spintronic devices, offering a pathway to robust and controllable magnetic behaviour.

Altermagnetism and Disorder in Materials

Recent work explores altermagnetism, a novel magnetic state, and its emergence in two-dimensional electron systems. Scientists investigate the conditions under which this unusual magnetic order arises, particularly in the presence of disorder and material anisotropy. Their research reveals that altermagnetism becomes favoured over conventional ferromagnetism as the strength of material anisotropy increases, and importantly, this state persists even in the presence of external magnetic fields. This discovery expands our understanding of magnetic ordering in materials and could prove significant for the development of future spintronic devices, offering a pathway to robust and controllable magnetic behaviour.

Altermagnetism Emerges From Anisotropic Electron Systems

This research establishes the possibility of altermagnetism within two-dimensional electron systems exhibiting anisotropic behaviour and subject to disorder. Scientists demonstrate that altermagnetism emerges as a favoured state over conventional ferromagnetism when anisotropy and interaction strength reach certain levels, particularly in the absence of spin-orbit coupling. The inclusion of spin-orbit coupling introduces a competing paramagnetic state, leading to a critical point that defines the transition between different magnetic orders. Importantly, the transition from the paramagnetic state to magnetic order is distinct from the transition between ferromagnetism and altermagnetism, indicating a complex interplay of magnetic interactions.

Altermagnetism Emerges From Paramagnetic Competition

This work investigates the emergence of altermagnetism in two-dimensional electron systems exhibiting anisotropic behaviour and subject to disorder. Scientists demonstrate that altermagnetism arises under specific conditions, particularly when the strength of interactions exceeds a critical point and in the absence of strong spin-orbit coupling. Data shows a second-order transition from the paramagnetic state to the magnetically ordered phase, and a first-order transition between the ferromagnetic and altermagnetic states. Crucially, the altermagnetic state proves robust against small magnetic fields, displaying a coexistence with field-induced magnetization.

Altermagnetism Emerges From Anisotropic Electron Systems

This research establishes the possibility of altermagnetism within two-dimensional electron systems exhibiting anisotropic behaviour and subject to disorder. Scientists demonstrate that altermagnetism emerges as a favoured state over conventional ferromagnetism when anisotropy and interaction strength reach certain levels, particularly in the absence of spin-orbit coupling. The inclusion of spin-orbit coupling introduces a competing paramagnetic state, leading to a critical point that defines the transition between different magnetic orders. Importantly, the team’s work reveals that altermagnetism is remarkably robust even in the presence of external magnetic fields, displaying a coexistence with induced magnetization.

Researchers analyzed the impact of disorder on the system, finding that the disorder remains invariant under certain symmetry operations, preventing the destruction of existing magnetic phases. Measurements confirm that the presence of altermagnetic order does not alter the localization properties of the system, maintaining standard diffusive behaviour. The study demonstrates that as the system approaches a metal-insulator transition, the effective coupling constant increases dramatically, driving the system into a strong coupling regime. This transition occurs at distances larger than the localization length, indicating a connection between altermagnetism and insulating behaviour in materials like disordered ruthenium oxide.

The team computed the effective k⋅p model and polarization function to understand the system’s behaviour, providing a detailed theoretical framework for analyzing the emergence of altermagnetism and its response to external stimuli. These calculations provide insights into the microscopic mechanisms driving the observed magnetic phases and their stability.