Broadband electron paramagnetic resonance of a molecular spin triangle

A new broadband EPR spectrometer capable of measuring in frequency- and field-sweep modes is described and its functionality is demonstrated on a ferromagnetic Cu3II triangle demonstrating a moderate zero-field splitting of its quartet ground state.

Constant-adiabaticity ultralow magnetic field manipulations of parahydrogen-induced polarization: application to an AA'X spin system

Magnetic field sweeps are used to transfer parahydrogen-induced polarization from hydrogen atoms onto heteronuclear spins such as carbon-13. In this work we describe and implement constant adiabaticity field sweep profiles for this purpose.

Polarization Transfer via Field Sweeping in Parahydrogen-Enhanced Nuclear Magnetic Resonance

<div><br></div><div><table><tr><td>We show that in a spin system of two magnetically inequivalent protons coupled to a heteronucleus such as 13C, an adiabatic magnetic field sweep, passing through zero field, transfers proton singlet order into magnetization of the coupled heteronucleus. This effect is potentially useful in parahydrogen-enhanced nuclear magnetic resonance, and is demonstrated on singlet-hyperpolarized [1-13C]maleic acid, which is prepared via the reaction between [1-13C]acetylene dicarboxylic acid and para-enriched hydrogen gas. The magnetic field sweeps are of microtesla amplitudes, and have durations on the order of seconds. We show a polarization enhancement by a factor of 10⁴ in the 13C spectra of [1-13C]maleic acid in a 1.4 T magnetic field.</td></tr></table></div>

Polarization Transfer via Field Sweeping in Parahydrogen-Enhanced Nuclear Magnetic Resonance

<div><br></div><div><table><tr><td>We show that in a spin system of two magnetically inequivalent protons coupled to a heteronucleus such as 13C, an adiabatic magnetic field sweep, passing through zero field, transfers proton singlet order into magnetization of the coupled heteronucleus. This effect is potentially useful in parahydrogen-enhanced nuclear magnetic resonance, and is demonstrated on singlet-hyperpolarized [1-13C]maleic acid, which is prepared via the reaction between [1-13C]acetylene dicarboxylic acid and para-enriched hydrogen gas. The magnetic field sweeps are of microtesla amplitudes, and have durations on the order of seconds. We show a polarization enhancement by a factor of 10⁴ in the 13C spectra of [1-13C]maleic acid in a 1.4 T magnetic field.</td></tr></table></div>

Hysteretic magnetoelectric behavior of CoFe2O4–BaTiO3 composites prepared by reductive sintering and reoxidation

Magnetoelectric composites (CoFe2O4)x–(BaTiO3)1-x with x = 0.1, 0.2, 0.3, 0.4 and 0.5 were prepared bya polyol mediated synthesis route. The densification step was performed in a reducing forming gasatmosphere at 1250 1C. Under these conditions Co2+ and Fe3+ are reduced to the corresponding metalsand thus a reaction of these elements with the BaTiO3 matrix is prevented. Reoxidation in air to CoFe2O4at a rather low temperature of 800 1C leads to samples free of secondary phases. While the course of thesynthesis was monitored by TGA, XRD and photometric analysis, the final composites were characterizedvia SEM, EDX, impedance spectroscopy and magnetic and magnetoelectric (ME) measurements. Allsamples show pronounced ME hystereses and aME maxima dependent on the Hdc field sweep direction.The sample with x = 0.4 exhibits the highest maximum aME of 420 mV Oe-1 cm-1.