Using X-ray absorption techniques, we show that temperature-and light-induced spin crossover properties are conserved for a sub-monolayer of the [Fe(H 2 B(pz) 2 ) 2 (2,2'-bipy)] complex evaporated onto a Au(111) surface. For a significant fraction of the molecules, we see changes in the absorption at the L 2,3 edges that are consistent with those observed in bulk and thick film references. Assignment of these changes to spin crossover is further supported by multiplet calculations to simulate the x-ray absorption spectra. As others have observed in experiments on monolayer coverages, we find that many molecules in our submonolayer system remain pinned in one of the two spin states. Our results clearly demonstrate that temperature-and light-induced spin-crossover is possible for isolated molecules on surfaces, but that interactions with the surface may play a key role in determining when this can occur. TOC X-ray absorption techniques evidenced that temperature-and light-induced spin crossover properties were conserved for a sub-monolayer of the [Fe(H 2 B(pz) 2 ) 2 (2,2'-bipy)] complex evaporated on a Gold surface KEYWORDS: spin crossover,·UHV evaporation,·submonolayer,·X-ray absorption,·iron complexes 3 Spin Crossover (SCO) complexes are promising building blocks for spintronic 1 Using variable temperature X-ray absorption spectra, we examined a submonolayer coverage evaporated in situ under UHV conditions on Au(111), before and after irradiation with visible laser light. We compare these results to those obtained from two other samples: 1) a 5 single crystal finely scratched on gold foil, which we use as a spectroscopic bulk reference; and 2) a 300 nm thick film sublimedex situ on copper foil, to check the preservation of structure and properties of the complex. Experimental spectra were then compared to the ones obtained using multiplet calculations. 37-39The variation of the L 2,3 edge spectra for the bulk sample over the range of the thermal spin crossover (100-300 K) is reported in Figure 1a(see also Figure S1 in Supplementary Information Spectra measured on the thick film prepared ex situ are similar to the bulk, and show comparable temperature dependence (Figure 1b and Figure S1). Nevertheless, the thick film spectrum is slightly differentfrom the bulk compound: shoulders on the high-energy side (at 300 K) or at the low-energy side (at 100 K) of the L 3 absorption peak, are likely associated with a small fraction of decomposition product, which maybe caused by air exposure of this sample prepared ex situ.The analysis of the temperature-dependent spectra as weighted sums of the bulk spectra at 300 K and 100 K, chosen as representative of the HS and LS state respectively, allows for the extraction of the temperature dependence of the HS fraction (Table S2). For the thick film, the shoulder signals were found to be temperature independent, and thus do not affect the switching behavior. We extracted this spurious contribution ( Figures S3 and S4) and subtracted it from all spectra before evaluating...

We report clean evaporation under ultra-high vacuum conditions of two spin crossover materials, yielding either microcrystallites or homogeneous thin films. Magnetic and photomagnetic studies show that thermal and light-induced spin crossover properties are preserved. Preliminary STM imaging of sub-monolayers indicates that the deposited molecules remain intact on the surface.

We study the spin dynamics in two variants of the high-anisotropy Mn6 nanomagnet by inelastic neutron scattering, magnetic resonance spectroscopy and magnetometry. We show that a giant-spin picture is completely inadequate for these systems and that excited S multiplets play a key role in determining the effective energy barrier for the magnetization reversal. Moreover, we demonstrate the occurrence of tunneling processes involving pair of states having different total spin.

The reaction of the hexacyanometalates K3[M(1)(CN)6] (M(1) = Cr(III), Fe(III), Co(III)) with the bispidine complexes [M(2)(L(1))(X)](n+) and [M(2)(L(2))(X)](n+) (M(2) = Mn(II), Ni(II), Cu(II); L(1) = 3-methyl-9-oxo-2,4-di-(2-pyridyl)-7-(2-pyridylmethyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylic acid dimethyl ester; L(2) = 3-methyl-9-oxo-7-(2-pyridylmethyl)-2,4-di-(2-quinolyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylic acid dimethyl ester; X = anion or solvent) in water-methanol mixtures affords trinuclear complexes with cis- or trans-arrangement of the bispidine-capped divalent metal centers around the hexacyanometalate. X-ray structural analyses of five members of this family of complexes (cis-Fe[CuL(2)]2, trans-Fe[CuL(1)]2, cis-Co[CuL(2)]2, trans-Cr[MnL(1)]2, trans-Fe[MnL(1)]2) and the magnetic data of the entire series are reported. The magnetic data of the cyanide bridged, ferromagnetically coupled cis- and trans-Fe[ML]2 compounds (M = Ni(II), Cu(II)) with S = 3/2 (Cu(II)) and S = 5/2 (Ni(II)) ground states are analyzed with an extended Heisenberg Hamiltonian which accounts for anisotropy and zero-field splitting, and the data of the Cu(II) systems, for which structures are available, are thoroughly analyzed in terms of an orbital-dependent Heisenberg Hamiltonian, in which both spin-orbit coupling and low-symmetry ligand fields are taken into account. It is shown that the absence of single-molecule magnetic behavior in all spin clusters reported here is due to a large angular distortion of the [Fe(CN)6](3-) center and the concomitant quenching of orbital angular momentum of the Fe(III) ((2)T2g) ground state.

Phenomena that are highly sensitive to magnetic fields can be exploited in sensors and non-volatile memories [1]. The scaling of such phenomena down to the single molecule level [2, 3] may enable novel spintronic devices [4]. Here we report magnetoresistance in a single molecule junction arising from negative differential resistance that shifts in a magnetic field at a rate two orders of magnitude larger than Zeeman shifts. This sensitivity to the magnetic field produces two voltage-tunable forms of magnetoresistance, which can be selected via the applied bias. The negative differential resistance is caused by transient charging [5][6][7] of an iron phthalocyanine (FePc) molecule on a single layer of copper nitride (Cu 2 N) on a Cu(001) surface, and occurs at voltages corresponding to the alignment of sharp resonances in the filled and empty molecular states with the Cu(001) Fermi energy. An asymmetric voltage-divider effect enhances the apparent voltage shift of the negative differential resistance with magnetic field, which inherently is on the scale of the Zeeman energy [8]. These results illustrate the impact that asymmetric coupling to metallic electrodes can have on transport through molecules, and highlight how this coupling can be used to develop molecular spintronic applications.Research into magnetoresistance [9, 10] has been driven by the widespread use of giant magnetoresistance (GMR) sensors in hard drives as well as other applications such as magnetoresistive random access memory (MRAM) [1]. To reach even higher storage densities, research has begun to concentrate on magnetoresistance at the atomic scale [2, 3, 11]. For a single molecule, however, the small area for enclosing flux and modest energy scales associated with electronic Zeeman shifts typically make it difficult to tune magnetoresistive phenomena with an external magnetic field.Another electron transport phenomenon with technological relevance is negative differential resistance (NDR) [5, 7,[12][13][14][15][16][17][18][19], in which an increase in voltage causes a decrease in current. Commercial devices, such as the resonant tunnelling diode, utilise these regions in specialised applications [20, 21]. Various mechanisms cause NDR at the atomic scale [5, 7,[12][13][14][15][16][17][18][19], though none are expected to have a magnetic field dependence that would shift the NDR on a scale larger than the Zeeman energy.Using low temperature scanning tunnelling microscopy (STM) (see Supplementary Methods), we observe an NDR effect for FePc molecules placed in a vacuum junction on top of 2 a Cu(001) surface capped with a single layer of Cu 2 N (Fig. 1). Cu 2 N is a thin insulator that can decouple the spins of magnetic atoms from the underlying surface [22]; FePc is a magnetic molecule that can be easily sublimed [23][24][25] and is observed to have interesting magnetic properties on thin insulating layers [26]. On Cu 2 N, FePc is centred above both Cu and N sites. The two binding sites can be differentiated using atomically resolved imaging a...

Torque magnetometry and far-infrared spectroscopy elucidate electronic structure and magnetic properties of Dy3 single molecule magnet.

The experimental investigation of the molecular magnetic anisotropy in crystals in which the magnetic centers are symmetry related, but do not have a parallel orientation has been approached by using torque magnetometry. A single crystal of the orthorhombic organometallic Cp*ErCOT [Cp*=pentamethylcyclopentadiene anion (C5Me5(-)); COT=cyclooctatetraenedianion (C8H8(2-))] single-molecule magnet, characterized by the presence of two nonparallel families of molecules in the crystal, has been investigated above its blocking temperature. The results confirm an Ising-type anisotropy with the easy direction pointing along the pseudosymmetry axis of the complex, as previously suggested by out-of-equilibrium angular-resolved magnetometry. The use of torque magnetometry, not requiring the presence of magnetic hysteresis, proves to be even more powerful for these purposes than standard single-crystal magnetometry. Furthermore, exploiting the sensitivity and versatility of this technique, magnetic anisotropy has been investigated up to 150 K, providing additional information on the crystal-field splitting of the ground J multiplet of the Er(III) ion.

The generation and control of fast switchable magnetic fields with large gradients on the nanoscale is of fundamental interest in material science and for a wide range of applications. However, it has not yet been possible to characterize those fields at high bandwidth with arbitrary orientations. Here, we measure the magnetic field generated by a hard-disk-drive write head with high spatial resolution and large bandwidth by coherent control of single electron and nuclear spins. We are able to derive field profiles from coherent spin Rabi oscillations close to the gigahertz range, measure magnetic field gradients on the order of 1 mT nm and quantify axial and radial components of a static and dynamic magnetic field independent of its orientation. Our method paves the way for precision measurement of the magnetic fields of nanoscale write heads, which is important for future miniaturization of these devices.