Creating a Ferromagnetic Ground State with Tc Above Room Temperature in a Paramagnetic Alloy through Non‐Equilibrium Nanostructuring. Issue 11 (6th February 2022)

• Record Type: Journal Article
• Authors: Ye, Xinglong; Fortunato, Nuno; Sarkar, Abhishek; Geßwein, Holger; Wang, Di; Chen, Xiang; Eggert, Benedikt; Wende, Heiko; Brand, Richard A.; Zhang, Hongbin; Hahn, Horst; Kruk, Robert
• Is Part Of: Advanced materials. Volume 34:Issue 11(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-06
• Subjects: FeRh alloys -- ferromagnetic materials -- magnetostructural coupling -- multiple ground states -- non‐equilibrium nanostructuring, paramagnetic materials; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.202108793
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: Materials with strong magnetostructural coupling have complex energy landscapes featuring multiple local ground states, thus making it possible to switch among distinct magnetic‐electronic properties. However, these energy minima are rarely accessible by a mere application of an external stimuli to the system in equilibrium state. A ferromagnetic ground state, with T c above room temperature, can be created in an initially paramagnetic alloy by nonequilibrium nanostructuring. By a dealloying process, bulk chemically disordered FeRh alloys are transformed into a nanoporous structure with the topology of a few nanometer‐sized ligaments and nodes. Magnetometry and Mössbauer spectroscopy reveal the coexistence of two magnetic ground states, a conventional low‐temperature spin‐glass and a hitherto‐unknown robust ferromagnetic phase. The emergence of the ferromagnetic phase is validated by density functional theory calculations showing that local tetragonal distortion induced by surface stress favors ferromagnetic ordering. The study provides a means for reaching conventionally inaccessible magnetic states, resulting in a complete on/off ferromagnetic–paramagnetic switching over a broad temperature range. Abstract : A hitherto‐unknown ferromagnetic ground state with Curie temperature above room temperature can be created in an initially paramagnetic alloy by non‐equilibrium nanostructuring. The ferromagnetic ground state originates from surface stress‐induced tetragonal distortion in the ligaments of the nanoporous network. The study demonstrates a route for reaching conventionally inaccessible magneto‐electronic states and achieving an on/off ferromagnetic–paramagnetic switching for potential applications.