Broadband electron paramagnetic resonance of a molecular spin triangle.

We built a broadband Electron Paramagnetic Resonance (EPR) spectrometer capable of field- and frequency sweep experiments under field-, microwave amplitude- and microwave frequency-modulation detection modes (HM, AM, and FM, respectively). The spectrometer is based on a coplanar waveguide (CPW) architecture, with the sample being deposited on top of the transmission line. We tested the functionality of this spectrometer by measuring a standard 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH) sample, and complex (NnBu4)2[Cu3(µ3-Cl)2(µ-pz)3Cl3] (1), drop-casted on the CPW. Complex 1 had been previously studied by conventional X-band EPR spectroscopy (Chem. - Eur. J., 2020, 26, 12769-1784), and comparison with the past studies validated the functionality of the spectrometer and confirmed the stability of the sample upon deposition. Moreover, our results highlighted the importance of surface effects and of the orientation of the microwave magnetic component B1 on the lineshapes of the recorded spectra.

Magnetic Control over the Fractal Dimension of Supramolecular Rod Networks.

Controlling supramolecular polymerization is of fundamental importance to create advanced materials and devices. Here we show that the thermodynamic equilibrium of Gd3+-bearing supramolecular rod networks is shifted reversibly at room temperature in a static magnetic field of up to 2 T. Our approach opens opportunities to control the structure formation of other supramolecular or coordination polymers that contain paramagnetic ions.

Current-induced spin-wave Doppler shift.

Spin transfer appears to be a promising tool for improving spintronics devices. Experiments that quantitatively access the magnitude of the spin transfer are required for a fundamental understanding of this phenomenon. By inductively measuring spin waves propagating along a permalloy strip subjected to a large electrical current, we observed a current-induced spin wave Doppler shift that we relate to the adiabatic spin transfer torque. Because spin waves provide a well-defined system for performing spin transfer, we anticipate that they could be used as an accurate probe of spin-polarized transport in various itinerant ferromagnets.

Micromagnetic phase transitions and spin wave excitations in a ferromagnetic stripe.

Magnetic excitations of micrometer-wide ferromagnetic stripes subjected to a transverse applied field have been measured between 1 and 20 GHz. The complexity of the observed response is attributed to the spatially nonuniform equilibrium spin distribution. This one is modeled analytically and numerically, which allows one to distinguish two micromagnetic phases governing the ground state. The nucleation-related phase transitions are evidenced by soft modes, while the different observed resonances are attributed to spin wave modes localized in the two phases and at their interface.