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In rare earth nickelates, the metal‐to‐insulator transition observed as a function of temperature can be described using an electronic and a structural order parameter. The electronic one is linked to the electronic disproportionation observed below the transition temperature and the structural one characterizes the breathing mode that develops in the low temperature phase. Here SmNiO3/NdNiO3 superlattices are grown with insulating LaAlO3 spacer layers to study the unusual coupling of metal‐to‐ insulator transitions observed at SmNiO3/NdNiO3 interfaces and determine the role of the two order parameters. Temperature‐dependent transport measurements reveal that a single unit cell of LaAlO3 inserted between SmNiO3 and NdNiO3 leads to a complete decoupling of the metal‐to‐insulator transitions suggesting that the order parameter controlling the coupling is the electronic one.

High‐sensitivity nanomechanical sensors are mostly based on silicon technology and related materials. The use of functional materials, such as complex oxides having strong interplay between structural, electronic, and magnetic properties, may open possibilities for developing new mechanical transduction schemes and for further enhancement of the device performances. The integration of these materials into micro/nano‐electro‐mechanical systems (MEMS/NEMS) is still at its very beginning and critical basic aspects related to the stress state and the quality factors of mechanical resonators made from epitaxial oxide thin films need to be investigated. Here, suspended micro‐bridges are realized from single‐crystal thin films of (La0.7,Sr0.3)MnO3 (LSMO), a prototypical complex oxide showing ferromagnetic ground state at room temperature. These devices are characterized in terms of resonance frequency, stress state, and Q‐factor. LSMO resonators are highly stressed, with a maximum value of ≈260 MPa. The temperature dependence of their mechanical resonance is discussed considering both thermal strain and the temperature‐dependent Young's modulus. The measured Q‐factors reach few tens of thousands at room temperature, with indications of further improvements by optimizing the fabrication protocols. These results demonstrate that complex oxides are suitable to realize high Q‐factor mechanical resonators, paving the way toward the development of full‐oxide MEMS/NEMS sensors.

Metal‐to‐Insulator Transitions In article number 2201291, Lucia Varbaro and co‐workers report on the growth and characterization of new nickelate based superlattices including insulating LaAlO3 spacer layers. This study allows the role of the electronic and structural order parameters, describing the metal‐to‐insulator transition, to be better understood in these complex heterostructures. Artistic view of the metallic phase and of the insulating one displaying a breathing distortion – Image credit: Xavier Ravinet.