Large Orbital Magnetic Moment in VI₃

The existence of the V3+-ion orbital moment is an open issue of the nature of magnetism in the van der Waals ferromagnet VI3. The huge magnetocrystalline anisotropy in conjunction with the significantly reduced ordered magnetic moment compared to the spin-only value provides strong but indirect evidence of a large V orbital moment. We used the unique capability of X-ray magnetic circular dichroism to determine the orbital component of the total magnetic moment and provide a direct proof of an exceptionally sizable orbital moment of the V3+ ion in VI3. Our ligand field multiplet simulations of the XMCD spectra in synergy with the results of DFT calculations agree with the existence of two V sites with different orbital occupations and OM magnitudes in the ground state

X‑ray Magnetic Circular Dichroism (XMCD) Study of a Methoxide-Bridged Dy^III–Cr^III Cluster Obtained by Fluoride Abstraction from <i>cis</i>-[Cr^IIIF₂(phen)₂]⁺

An isostructural series of dinuclear chromium­(III)–lanthanide­(III) clusters is formed by fluoride abstraction of <i>cis</i>-[CrF₂(phen)₂]⁺ by Ln³⁺ resulting in LnF₃ and methoxide-bridged Cr–Ln clusters (Ln = Nd (<b>1</b>), Tb (<b>2</b>), Dy (<b>3</b>)) of formula [Cr^III(phen)₂(μ-MeO)₂Ln­(NO₃)₄]·<i>x</i>MeOH (<i>x</i> = 2–2.73). In contrast to fluoride, methoxide bridges in a nonlinear fashion, which facilitates chelation. For <b>3</b>, X-ray magnetic circular dichroism (XMCD) provides element-specific magnetization curves that are compared to cluster magnetization and susceptibility data acquired by SQUID magnetometry. The combination of XMCD and SQUID is able to resolve very small magnetic coupling values and reveals a weak Cr^III–Dy^III coupling of <i>j</i> = −0.04(3) cm^–1. The Dy^III ion has a ground-state Kramers doublet of <i>m</i>_<i>J</i> = ±13/2, and the first excited doublet is found to be <i>m</i>_<i>J</i> = ±11/2 at an energy of δ = 57(21) cm^–1. The Cr^III ion exhibits a uniaxial anisotropy of <i>D</i>_Cr = −1.7(1.0) cm^–1. Further, we observe that a weak anisotropic coupling of dipolar origin is sufficient to model the data, suggesting that methoxide bridges do not play a significant role in the magnetic coupling for the present systems

Reduction of Mn₁₉ Coordination Clusters on a Gold Surface

The magnetic properties of a Mn₁₉ coordination cluster equipped with methylmercapto substituents on the organic ligands, [Mn^III₁₂Mn^II₇​(μ₄-O)₈​(μ₃-Cl)_7.7​(μ₃-OMe)_0.3​(HL^SMe)₁₂​(MeOH)₆]­Cl₂·27MeCN (Mn₁₉(SMe)) (H₃L^SMe = 2,6-bis­(hydroxy­methyl)-4-mercapto­methyl­phenol) deposited on Au(111) surfaces from solution, have been investigated by X-ray absorption spectroscopy and X-ray magnetic circular dichroism. The data reveal that in the submonolayer regime the molecules contain only divalent Mn^II in contrast to the presence of Mn^II and Mn^III ions in the powder sample. Brillouin function fits to the field-dependent magnetization suggest that the total spin ground state in the submonolayer is much lower than <i>S</i>_TOT = 83/2 of the pristine molecules. These findings suggest that significant changes of the electronic structure, molecular geometry, and intramolecular exchange coupling take place upon surface deposition. A sample with coverage of 2–3 monolayers shows the presence of Mn^III, suggesting that a decoupling layer could stabilize the Mn₁₉ core on a metallic surface

An Endohedral Single-Molecule Magnet with Long Relaxation Times: DySc₂N@C₈₀

The magnetism of DySc₂N@C₈₀ endofullerene was studied with X-ray magnetic circular dichroism (XMCD) and a magnetometer with a superconducting quantum interference device (SQUID) down to temperatures of 2 K and in fields up to 7 T. XMCD shows hysteresis of the 4f spin and orbital moment in Dy^III ions. SQUID magnetometry indicates hysteresis below 6 K, while thermal and nonthermal relaxation is observed. Dilution of DySc₂N@C₈₀ samples with C₆₀ increases the zero-field 4f electron relaxation time at 2 K to several hours

Exchange Interaction of Strongly Anisotropic Tripodal Erbium Single-Ion Magnets with Metallic Surfaces

We present a comprehensive study of Er(trensal) single-ion magnets deposited in ultrahigh vacuum onto metallic surfaces. X-ray photoelectron spectroscopy reveals that the molecular structure is preserved after sublimation, and that the molecules are physisorbed on Au(111) while they are chemisorbed on a Ni thin film on Cu(100) single-crystalline surfaces. X-ray magnetic circular dichroism (XMCD) measurements performed on Au(111) samples covered with molecular monolayers held at temperatures down to 4 K suggest that the easy axes of the strongly anisotropic molecules are randomly oriented. Furthermore XMCD indicates a weak antiferromagnetic exchange coupling between the single-ion magnets and the ferromagnetic Ni/Cu(100) substrate. For the latter case, spin-Hamiltonian fits to the XMCD <i>M</i>(<i>H</i>) suggest a significant structural distortion of the molecules. Scanning tunneling microscopy reveals that the molecules are mobile on Au(111) at room temperature, whereas they are more strongly attached on Ni/Cu(100). X-ray photoelectron spectroscopy results provide evidence for the chemical bonding between Er(trensal) molecules and the Ni substrate. Density functional theory calculations support these findings and, in addition, reveal the most stable adsorption configuration on Ni/Cu(100) as well as the Ni–Er exchange path. Our study suggests that the magnetic moment of Er(trensal) can be stabilized <i>via</i> suppression of quantum tunneling of magnetization by exchange coupling to the Ni surface atoms. Moreover, it opens up pathways toward optical addressing of surface-deposited single-ion magnets

Orientation-Driven Strong Perpendicular Magnetic Anisotropy in La_0.67Sr_0.33MnO₃–SrIrO₃ Heterostructures

Strong perpendicular magnetic anisotropy (PMA) is crucial for high-performance spintronic devices. However, in transition-metal oxides, it is challenging to achieve an excellent PMA property (anisotropy energy, KU > 106 erg/cm3), limiting their application potential. Here, we report a pathway to achieve obvious PMA in 3d–5d [nLa0.67Sr0.33MnO3,nSrIrO3]m ([nLSMO, nSIO]m) heterostructures via the cooperation of interfacial engineering and crystal orientation. By depositing multilayers with a (110) orientation, significant PMA is observed despite the fact that the bare LSMO and (001)-oriented heterostructures show in-plane magnetic anisotropy. First-principles calculations suggest that in the (110)-oriented heterosystems, SIO exhibits a large and perpendicular single-ion anisotropy attributed to its strong spin–orbit coupling effect, which leads to the PMA through strong orbital hybridization between Mn and Ir ions at the LSMO/SIO interface. By varying thicknesses (n) of LSMO and SIO, the KU can be optimized to 4 × 106 erg/cm3. Moreover, the conductive behavior can also be drastically altered between insulation and metallicity with the n change, implying the potential for simultaneously obtaining ferromagnetic metals and insulators with sizable PMA in one oxide heterosystem. These findings highlight the importance of interfacial engineering and crystalline orientation in tuning PMA in oxides and provide a feasible route for developing high-performance oxide-based spintronic devices