H.-A. Krug von Nidda

Relaxor ferroelectricity and colossal magnetocapacitive coupling in ferromagnetic CdCr2S4

Materials in which magnetic and electric order coexist—termed ‘multiferroics’ or ‘magnetoelectrics’—have recently become the focus of much research. In particular, the simultaneous occurrence of ferromagnetism and ferroelectricity, combined with an intimate coupling of magnetization and polarization via magnetocapacitive effects, holds promise for new generations of electronic devices. Here we present measurements on a simple cubic spinel compound with unusual, and potentially useful, magnetic and electric properties: it shows ferromagnetic order coexisting with relaxor ferroelectricity (a ferroelectric cluster state with a smeared-out phase transition), both having sizable ordering temperatures and moments. Close to the ferromagnetic ordering temperature, the magnetocapacitive coupling (characterized by a variation of the dielectric constant in an external magnetic field) reaches colossal values, approaching 500 per cent. We attribute the relaxor properties to geometric frustration, which is well known for magnetic moments but here is found to impede long-range order of the structural degrees of freedom that drive the formation of the ferroelectric state.

Structural, magnetic, and electrical properties of single-crystalline La 1 − x Sr x MnO 3 ( 0.4 x 0.85 )

We report on structural, magnetic, and electrical properties of Sr-doped

Spin and orbital frustration in MnSc2S4 and FeSc2S4.

{\mathrm{LaMnO}}_{3}

Orbital freezing and orbital glass state in FeCr2S4.

single crystals for doping levels

Spin-driven phonon splitting in bond-frustrated ZnCr2S4.

0.4l~xl~0.85.

Experimental observation of the triplet spin-valve effect in a superconductor-ferromagnet heterostructure

The complex structural and magnetic phase diagram can only be explained assuming significant contributions from the orbital degrees of freedom. Close to

Ferromagnetic resonance studies of (Ga,Mn)As with MnAs clusters

x=0.6

Anisotropic exchange inLiCuVO4probed by ESR

a ferromagnetic metal is followed by an antiferromagnetic metallic phase below 200 K. This antiferromagnetic metallic phase exists in a monoclinic crystallographic structure. Following theoretical predictions this metallic antiferromagnet is expected to reveal an

Switching the ferroelectric polarization in theS=1∕2chain cuprateLiCuVO4by external magnetic fields

{(x}^{2}\ensuremath{-}{y}^{2})

Anisotropy of the magnetotransport in (Ga,Mn)As/MnAs paramagnetic-ferromagnetic hybrid structures

-type orbital order. For higher Sr concentrations an antiferromagnetic insulator is established below room temperature.