J. Hemberger

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.

Observation of a griffiths phase in paramagnetic La1-xSrxMnO3.

We report on the discovery of a novel triangular phase regime in the system La1-xSrxMnO3 by means of electron spin resonance and magnetic susceptibility measurements. This phase is characterized by the coexistence of ferromagnetic entities within the globally paramagnetic phase far above the magnetic ordering temperature. The nature of this phase can be understood in terms of Griffiths singularities arising due to the presence of correlated quenched disorder in the orthorhombic phase.

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

Colossal Magnetocapacitance and Colossal Magnetoresistance in HgCr2S4

{\mathrm{LaMnO}}_{3}

Multiferroic phases of Eui_xYxMnO3

single crystals for doping levels

Charge carrier localization in investigated by ac conductivity measurements

0.4l~xl~0.85.

Spin and orbital frustration in MnSc2S4 and FeSc2S4.

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

Quantum paraelectric and induced ferroelectric states in

x=0.6

Magnetic properties and the phase diagram of La1-xSrxMnO3 for x ≤ 0.2

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

Quantum paraelectric and induced ferroelectric states in SrTiO3

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