Electronically ordered ultrathin Cr2O3 on Pt(1 1 1) in presence of a multidomain graphene intralayer

In the last decade, reducing the dimensionality of materials to few atomic layers thickness has allowed exploring new physical properties and functionalities otherwise absent out of the two dimensional limit. In this regime, interfaces and interlayers play a crucial role. Here, we investigate their influence on the electronic properties and structural quality of ultrathin Cr2O3 on Pt(111), in presence of a multidomain graphene intralayer. Specifically, by combining Low-Energy Electron Diffraction, X-ray Photoelectron Spectroscopy and X-ray Absorption Spectroscopy, we confirm the growth of high-quality ultrathin Cr2O3 on bare Pt, with sharp surface reconstructions, proper stoichiometry and good electronic quality. Once a multidomain graphene intralayer is included at the metal/oxide interface, the Cr2O3 maintained its correct stoichiometry and a comparable electronic quality, even at the very first monolayers, despite the partially lost of the morphological long-range order. These results show how ultrathin Cr2O3 films are slightly affected by the interfacial epitaxial quality from the electronic point of view, making them potential candidates for graphene-integrated heterostructures

Visible Light Effects on Photostrictive/Magnetostrictive PMN‐PT/Ni Heterostructure

The possibility of modifying the ferromagnetic response of a multiferroic heterostructure via fully optical means exploiting the photovoltaic/photostrictive properties of the ferroelectric component is an effective method for tuning the interfacial properties. In this study, the effects of 405 nm visible-light illumination on the ferroelectric and ferromagnetic responses of (001) Pb(Mg1/3Nb2/3)O-3-0.4PbTiO(3) (PMN-PT)/Ni heterostructures are presented. By combining electrical, structural, magnetic, and spectroscopic measurements, how light illumination above the ferroelectric bandgap energy induces a photovoltaic current and the photostrictive effect reduces the coercive field of the interfacial magnetostrictive Ni layer are shown. Firstly, a light-induced variation in the Ni orbital moment as a result of sum-rule analysis of x-ray magnetic circular dichroic measurements is reported. The reduction of orbital moment reveals a photogenerated strain field. The observed effect is strongly reduced when polarizing out-of-plane the PMN-PT substrate, showing a highly anisotropic photostrictive contribution from the in-plane ferroelectric domains. These results shed light on the delicate energy balance that leads to sizeable light-induced effects in multiferroic heterostructures, while confirming the need of spectroscopy for identifying the physical origin of interface behavior

Covalency, correlations, and interlayer interactions governing the magnetic and electronic structure of Mn3Si2Te6

Mn3Si2Te6 is a rare example of a layered ferrimagnet. It has recently been shown to host a colossal angular magnetoresistance as the spin orientation is rotated from the in- to out-of-plane direction, proposed to be underpinned by a topological nodal-line degeneracy in its electronic structure. Nonetheless, the origins of its ferrimagnetic structure remain controversial, while its experimental electronic structure, and the role of correlations in shaping this, are little explored to date. Here, we combine x-ray and photoemission-based spectroscopies with first-principles calculations to probe the elemental-selective electronic structure and magnetic order in Mn3Si2Te6. Through these, we identify a marked Mn-Te hybridization, which weakens the electronic correlations and enhances the magnetic anisotropy.We demonstrate how this strengthens the magnetic frustration in Mn3Si2Te6, which is key to stabilizing its ferrimagnetic order, and find a crucial role of both exchange interactions extending beyond nearest-neighbors and antisymmetric exchange in dictating its ordering temperature. Together, our results demonstrate a powerful methodology of using experimental electronic structure probes to constrain the parameter space for first-principles calculations of magnetic materials, and through this approach, reveal a pivotal role played by covalency in stabilizing the ferrimagnetic order in Mn3Si2Te6

Hexaaquamanganese(II) dinitrate bis-(hexamethylenetetramine) tetrahydrate

In the title compound, $[Mn(H-2O)_6](NO_3)_2.2C_6H_{12}N_4.4H_2O,$ the hexamethyleneteramine molecules have no direct coordination to the $Mn^{II}$ atom. $O-H\cdot\cdot\cdot{O}$ and $O-H\cdot\cdot\cdot{N}$ intermolecular hydrogen bonds form a three-dimensional network

Hexaaquanickel(II) dichromate bis(hexa-methylenetetramine) monohydrate

A novel compound consisting of a hydrated metal cation, an organic molecule, an inorganic complex anion and water of crystallization has been synthesized and is found to crystallize in the monoclinic space group $P2_1/c$. The structure of the title compound, $[Ni(H_2O)_6][Cr_2O_7]\cdot 2 C_6H_{12}N4 \cdot H_2O$, contains octahedrally coordinated nickel ions and discrete dichromate anions. The hexamethylenetetramine molecules have no direct coordination to the metal ions. There are two cations, two anions, four tetramine molecules and two uncoordinated water molecules in the asymmetric unit. The structure is stabilized by extensive intra- and intermolecular hydrogen bonding

Synthesis, characterization and structure of [Ni(H2O)6]2(Cr2O7)2(hmta)4⋅2H2O[Ni(H_2O)_6]_2(Cr_2O_7)_2(hmta)_4·2H_2O (hmta=hexamethylenetetramine): a novel metal organic–inorganic hybrid

A metal organic–inorganic hybrid compound $[Ni(H_2O)_6]_2(Cr_2O_7)_2(hmta)_4 2H_2O$ was prepared and characterized by single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group $P2_1/c$ with a = 7.976(5)A, b= 13.333(3)A, c= 14.070(3)A,\beta = 97.891(3); Z= 4 and R= 0.048. The structure consists of octahedrally coordinated nickel ions with water and discrete units of dichromate ions in which chromium is tetrahedrally coordinated. This inorganic moiety is well separated in the crystal structure from the organic moiety built by ‘‘hmta’’ ligands, resulting in the formation of a novel organic–inorganic framework

Synthesis and crystal structure of M(hmt)<SUB>2</SUB>(H<SUB>2</SUB>O)<SUB>6</SUB>(NO<SUB>3</SUB>)<SUB>2</SUB>.4H<SUB>2</SUB>O complexes, where M=Mn<SUP>2+</SUP>, Co<SUP>2+</SUP>

A series of M-hmt complexes, where M=Mn2+, Co2+ were synthesized and studied by single crystal X-ray diffraction. The cobalt complex crystallizes in the triclinic space group P-1 with a = 9.9098(2) &#197;, b = 9.390(2)&#197;, c = 9.649(2)&#197;, &#945;=88.3(1)&#176;, &#946;=75.6(2)&#176;, &#947;=61.64(3)&#176; with Z=1. The Mn complex crystallized in the monoclinic space group P21/n with , a = 9.511(3)&#197;, b = 16.232(4)&#197;, c= 19.426(5)&#197;, &#946;=90.6(4)&#176; with Z=4. The structure consists of hexa-coordinated metal cations with water as the ligand having slightly distorted octahedral geometry. The organic ligand, hexamethylenetetramine is not directly coordinated to the metal ion but its presence stabilizes the molecular assembly because of the presence of a rich variety of intermolecular interactions

Synthesis, characterization and structure of [Ni(H<SUB>2</SUB>O)<SUB>6</SUB>]<SUB>2</SUB>(Cr<SUB>2</SUB>O<SUB>7</SUB>)<SUB>2</SUB>(hmta)<SUB>4</SUB>&#183;2H<SUB>2</SUB>O (hmta=hexamethylenetetramine): a novel metal organic-inorganic hybrid

A metal organic-inorganic hybrid compound [Ni(H2O)6]2(Cr2O7)2(hmta)4&#183;2H2O was prepared and characterized by single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P21/c with a = 7.976(5)&#197;, b = 13.333(3)&#197;, c = 14.070(3)&#197;, &#946;=97.89&#176;(3), Z=4 and R=0.048. The structure consists of octahedrally coordinated nickel ions with water and discrete units of dichromate ions in which chromium is tetrahedrally coordinated. This inorganic moiety is well separated in the crystal structure from the organic moiety built by "hmta" ligands, resulting in the formation of a novel organic-inorganic framework

Covalency, correlations, and interlayer interactions governing the magnetic and electronic structure of Mn₃Si₂Te₆

Mn3Si2Te6 is a rare example of a layered ferrimagnet. It has recently been shown to host a colossal angular magnetoresistance as the spin orientation is rotated from the in- to out-of-plane direction, proposed to be underpinned by a topological nodal-line degeneracy in its electronic structure. Nonetheless, the origins of its ferrimagnetic structure remain controversial, while its experimental electronic structure, and the role of correlations in shaping this, are little explored to date. Here, we combine x-ray and photoemission-based spectroscopies with first-principles calculations, to probe the elemental-selective electronic structure and magnetic order in Mn3Si2Te6. Through these, we identify a marked Mn-Te hybridization, which weakens the electronic correlations and enhances the magnetic anisotropy. We demonstrate how this strengthens the magnetic frustration in Mn3Si2Te6, which is key to stabilizing its ferrimagnetic order, and find a crucial role of both exchange interactions extending beyond nearest-neighbours and anti-symmetric exchange in dictating its ordering temperature. Together, our results demonstrate a powerful methodology of using experimental electronic structure probes to constrain the parameter space for first-principles calculations of magnetic materials, and through this approach, reveal a pivotal role played by covalency in stabilizing the ferrimagnetic order in Mn3Si2Te6