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Reversible control of magnetization by electric fields without assistance from a subsidiary magnetic field or electric current could help reduce the power consumption in spintronic devices. When increasing temperature above room temperature, FeRh displays an uncommon antiferromagnetic to ferromagnetic phase transition linked to a unit cell volume expansion. Thus, using the strain exerted by an adjacent piezoelectric layer, the relative amount of antiferromagnetic and ferromagnetic regions can be tuned by an electric field applied to the piezoelectric material. Indeed, large variations in the saturation magnetization have been observed when straining FeRh films grown on suitable piezoelectric substrates. In view of its applications, the variations in the remanent magnetization rather than those of the saturation magnetization are the most relevant. Here, we show that in the absence of any bias external magnetic field, permanent and reversible magnetization changes as high as 34% can be induced by an electric field, which remain after this has been zeroed. Bulk and local magnetoelectric characterization reveals that the fundamental reason for the large magnetoelectric response observed at remanence is the expansion (rather than the nucleation) of ferromagnetic nanoregions. ; Financial support by the Spanish Government [Projects MAT2014-56063-C2-1-R, MAT2015-73839-JIN, MAT2014-51778-C2-1-R, MAT2015-64110-C2-2-R and MAT2017-86357-C3-1-R, and associated FEDER], the Generalitat de Catalunya (2017-SGR-1377, 2017-SGR-292), and the European Research Council (SPIN-PORICS 2014-Consolidator Grant, Agreement nº 648454) is acknowledged. We also acknowledge support from EU ERC Advanced Grant No. 268066, from the Ministry of Education of the Czech Republic Grant No. LM2011026, from the Grant Agency of the Czech Republic Grant no. 14-37427. ICMAB-CSIC authors acknowledge financial support from the Spanish Ministry of Economy and Competitiveness, through the "Severo Ochoa" Program for Centers of Excellence in R&D (SEV- 2015-0496). I.F. acknowledges Ramon y Cajal contract RYC-2017-22531. ; Peer reviewed

Steady or dynamic magnetoelectric response, selectable and adjustable by only varying the amplitude of the applied electric field, is found in a multiferroic FeRh/PMN-PT device. In-operando time-dependent structural, ferroelectric, and magnetoelectric characterizations provide evidence that, as in magnetic shape memory martensitic alloys, the observed distinctive magnetoelectric responses are related to the time-dependent relative abundance of antiferromagnetic−ferromagnetic phases in FeRh, unbalanced by voltagecontrolled strain. This flexible magnetoelectric response can be exploited not only for energy-efficient memory operations but also in other applications, where multilevel and/or transient responses are required. ; Financial support by the Spanish Government [Projects MAT2014-56063-C2-1-R, MAT2015- 73839-JIN, MAT2014-51778-C2-1-R and MAT2014-57960-C3-1-R, MAT2015-64110-C2-2-P, and associated FEDER], the Generalitat de Catalunya (2014-SGR-734, 2014-SGR-1015) and the European Research Council (SPIN-PORICS 2014-Consolidator Grant, Agreement nº 648454) is acknowledged. We also acknowledge support from the EU ERC Advanced Grant No. 268066, from the Ministry of Education of the Czech Republic Grant No. LM2011026, from the Grant Agency of the Czech Republic Grant no. 14-37427. ICMAB-CSIC authors acknowledge financial support from the Spanish Ministry of Economy and Competitiveness, through the "Severo Ochoa" Programme for Centres of Excellence in R&D (SEV- 2015-0496). IF acknowledges Juan de la Cierva – Incorporación postdoctoral fellowship (IJCI-2014-19102) from the Spanish Ministry of Economy and Competitiveness. Jose Santiso and Jose Manuel Caicedo Roque from Institut Català de Nanociència i Nanotecnologia are acknowledged for valuable collaboration on time-dependent X-ray characterization. We also acknowledge Max Stengel and Umesh Bhaskar for fruitful discussions. ; Peer reviewed

This work has been carried out under the support of Spanish Ministry of Science and Innovation under Projects MAT2016-76824-C3-1-R, PID2019-108075RB-C31/ AEI / 10.13039/501100011033 and PGC2018-097789-B-I00 and the Regional Government of Madrid under Project S2018/NMT-4321 NANOMAGCOST-CM. LA and MF acknowledge project RTI2018-095303-B-C53.

Among metamagnetic materials, FeRh alloys are technologically appealing due to their uncommon antiferromagnetic-to-ferromagnetic metamagnetic transition which occurs at a temperature T* just above room temperature. Here, a controlled increase of T* (DT* B 20 8C) is induced in pre-selected regions of FeRh films via mechanical strain nanopatterning. Compressive stresses generated at the vicinity of predefined nanoindentation imprints cause a local reduction of the FeRh crystallographic unit cell parameter, which leads to an increase of T* in these confined micro-/nanometric areas. This enhances the stability of the antiferromagnetic phase in these localized regions. Remarkably, generation of periodic arrays of nanopatterned features also allows modifying the overall magnetic and electric transport properties across large areas of the FeRh films. This approach is highly appealing for the design of new memory architectures or other AFM-spintronic devices. ; Dr Patxi Lo´pez-Barbera´ is acknowledged for his assistance with the MOKE experiments. Vicente Garcı´a-Juez from Real Casa de la Moneda – Fa´brica Nacional de Moneda y Timbre is acknowledged for his scientific advice. Dr Florencio Sa´nchez is acknowledged for the growth of the samples. Dr Bernat Bozzo is acknowledged for the electric transport characterization. ALBA synchrotron is acknowledged for the provision of beamtime at the MSPD (proposal number 2017092412) and CIRCE (proposal numbers 2017092462 and 2018022818) beamlines. Financial support from the Spanish Ministry of Economy and Competitiveness, through the ''Severo Ochoa'' Programme for Centres of Excellence in R&D (SEV-2015-0496 and SEV-2017-0706) and the MAT2017-85232-R, RTI2018-095303-B-C53. MAT2014-56063-C2-1- R, MAT2017-86357-C3-1-R (and associated FEDER) and MAT2015- 73839-JIN projects, the Generalitat de Catalunya (2014 SGR 734 and 2017 SGR 292), AGAUR (2018 LLAV 00032 and 2019 LLAV 00050) and the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 665919 is acknowledged. This work was supported by the European Research Council under the SPIN-PORICS 2014- Consolidator Grant, Agreement No. 648454 and the MAGICSWITCH 2019-Proof of Concept Grant, Agreement No. 875018. ICN2 is funded by the CERCA Programme/Generalitat de Catalunya. I. F. acknowledges his RyC contract RYC-2017-22531. E. C. acknowledges the partial financial support from the National Science Centre of Poland (NCN) by the PRELUDIUM project UMO-2015/17/N/ST5/01988 and the SONATA Project No. UMO-2016/23/D/ST3/02121. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). ; Peer reviewed

Metal halides are a class of layered materials with promising electronic and magnetic properties persisting down to the two-dimensional limit. While most recent studies focused on the trihalide components of this family, the rather unexplored metal dihalides are also van der Waals layered systems with distinctive magnetic properties. Here we show that the dihalide NiBr2 grows epitaxially on a Au(111) substrate and exhibits semiconducting and magnetic behavior starting from a single layer. Through a combination of a low-temperature scanning-tunneling microscopy, low-energy electron diffraction, X-ray photoelectron spectroscopy, and photoemission electron microscopy, we identify two competing layer structures of NiBr2 coexisting at the interface and a stoichiometrically pure layer-by-layer growth beyond. Interestingly, X-ray absorption spectroscopy measurements revealed a magnetically ordered state below 27 K with in-plane magnetic anisotropy and zero-remanence in the single layer of NiBr2/Au(111), which we attribute to a noncollinear magnetic structure. The combination of such two-dimensional magnetic order with the semiconducting behavior down to the 2D limit offers the attractive perspective of using these films as ultrathin crystalline barriers in tunneling junctions and low-dimensional devices. ; D.B. acknowledges funding from the Austrian Science Fund (FWF) under the Erwin Schrödinger fellowship agreement (project number: J4395-N). C.G.-O. and M.P.-D. acknowledge funding of the Ph.D. fellowship from the MPC Foundation. We gratefully acknowledge financial support from Spanish AEI (Grant Nos. PID2019-107338RB-C6, RTI-2018-095303-C53, and the Maria de Maeztu Units of Excellence Programme MDM-2016-0618) and from the European Union (EU) through Horizon 2020 (SUPERTED Grant No. 800923), from Interred POCTEFA V-A Spain/France/Andorra Program (EFA 194/16/TNSI), the Basque Government (GV/EJ) under grants IT-1255-19, and the European Regional Development Fund. P.G. acknowledges funding from MINECO Grant No. FIS2016-78591-C3-2-R and FLAG-ERA Grant No. PCI2019-111908-2. ; Peer reviewed

The fabrication of van der Waals heterostructures, artificial materials assembled by individual stacking of 2D layers, is among the most promising directions in 2D materials research. Until now, the most widespread approach to stack 2D layers relies on deterministic placement methods, which are cumbersome and tend to suffer from poor control over the lattice orientations and the presence of unwanted interlayer adsorbates. Here, we present a different approach to fabricate ultrathin heterostructures by exfoliation of bulk franckeite which is a naturally occurring and air stable van der Waals heterostructure (composed of alternating SnS 2-like and PbS-like layers stacked on top of each other). Presenting both an attractive narrow bandgap (<0.7 eV) and p-type doping, we find that the material can be exfoliated both mechanically and chemically down to few-layer thicknesses. We present extensive theoretical and experimental characterizations of the material's electronic properties and crystal structure, and explore applications for near-infrared photodetectors ; A.C.-G. acknowledges financial support from the BBVA Foundation through the fellowship 'I Convocatoria de Ayudas Fundacion BBVA a Investigadores, Innovadores y Creadores Culturales' ('Semiconductores ultradelgados: hacia la optpelectronica flexible'), from the MINECO (Ramón y Cajal 2014 program, RYC-2014-01406), from the MICINN (MAT2014-58399-JIN) and from European Commission under the Graphene Flagship, contract CNECTICT-604391. E.M.P. acknowledges financial support from the European Research Council (MINT, ERC-StG-307609) and from the MINECO of Spain (CTQ2014-60541-P). E.G. gratefully acknowledges the AMAROUT II fellowship program for receiving a grant for transnational mobility (Marie Curie Action, FP7-PEOPLE- 2011-COFUND (291803)). A.J.M.-M., G.R.-B. and N.A. acknowledge the support of the MICCINN/MINECO (Spain) through the programmes MAT2014-57915-R, BES-2012-057346 and FIS2011-23488 and Comunidad de Madrid (Spain) through the programme S2013/MIT-3007 (MAD2D). J.O.I. and H.S.J.v.d.Z. acknowledge the support of the Dutch organization for Fundamental Research on Matter (FOM) and by the Ministry of Education, Culture, and Science (OCW). M.A.N. acknowledeges the support of the MICCINN/MINECO (Spain) through the programmes MAT2013-49893-EXP and MAT2014-59315-R. Authors M.A.N., A.J.M.-M. and A.C.-G. acknowledge the support from ALBA Synchrotron for the experiments performed at Circe beamline (BL24-CIRCE) at ALBA Synchrotron with the collaboration of ALBA staff (proposal ID 2015091399). W.S.P. acknowledges CAPES Foundation, Ministry of Education of Brazil, under grant BEX 9476/13-0. W.S.P. and J.J.P. acknowledge MICCINN/MINECO (Spain) for financial support under grant FIS2013-47328-C02-1; the European Union structural funds and the Comunidad de Madrid MAD2D-CM programme under grant nos. P2013/MIT-3007 and P2013/MIT-2850; the Generalitat Valenciana under grant no. PROMETEO/2012/011