A direct electrocaloric effect (ECE) measurement system, based on a modified-differential scanning calorimeter (DSC), allowing the acquisition of both thermal (ECE, heat capacity) and electrical (P-E loops, leakage current) information simultaneously, was used to analyze 〈001〉-oriented PbMg1/3Nb2/3O3-30PbTiO3 single crystals. Different electric-field-induced phase transitions were identified on direct ECE measurements and confirmed by dielectric measurements. The strongest ECE (ΔTEC = 0.65 K) was measured for an applied electric field E = 10 kV/cm just above the temperature of depolarization. The direct ECE measurements were compared with indirect measurements obtained from dielectric polarization measurements versus electric field and temperature and a very good agreement was found. A region with negative ΔTEC was identified by both direct and indirect measurements. This phenomenon was attributed to the formation of a reversible field-induced phase transition towards a state with a different polar direction.

An analysis of Mn substitution in SrTiO3 is performed in order to understand the origin of reported spin coupling in lightly Mn‐doped SrTiO3. The spin glass state magnetoelectrically coupled to the dipolar glass state has previously been reported for SrTiO3 substituted with only 2% of Mn on the B‐site. An analysis of the substitution mechanism for A‐ and B‐site doping shows a strong influence of processing conditions, such as processing temperature, oxygen partial pressure, and off‐stoichiometry. The required conditions for a site‐selective substitution are defined, which yield a single‐phase and almost defect‐free perovskite. Magnetic measurements show no magnetic anomalies resulting from spin coupling and only a simple paramagnetic behavior. Magnetic anomalies are observed only for the samples in which Mn is misplaced within the cation sublattice of the SrTiO3 perovskite. This occurs due to improper material processing, which causes initially unpredicted changes in the valence state of the Mn and results in the formation of structural defects and irregularities associated with segregation and nucleation of the magnetic species. Previously reported spin coupling in Mn‐doped SrTiO3 is not an intrinsic phenomenon and cannot be treated as a spin glass.

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A quantitative assessment of the Raman spectrum emitted from a coarse-grained polycrystal of multiferroic BiFeO 3 has been carried out by means of a polarized Raman microprobe. The dependence of the intensity of Raman phonon modes has been first theoretically modeled as a function of crystal rotation. Then, the Raman tensor elements have been experimentally determined from the analysis of the A g and E g vibrational modes.

The highly anisotropic electrocaloric effect, evidenced by both direct measurements and a descriptive theoretical model in lead‐free relaxor ferroelectric Sr0.75Ba0.25Nb2O6 single crystals, can be exploited by producing low‐cost grain‐oriented ceramics. Combined with the broad‐temperature‐range cooling regime provided by their polar nanoregions, these materials may be the key to future cost‐ and energy‐efficient solid‐state refrigeration.

In functional oxide materials so‐called molecular auxetic behavior is extremely rare. Here, it is reported in the CoFe2O4 spinel structure. A CoFe2O4 epitaxial thin film under compressive axial strain also reduces its cell dimensions in the transverse direction with a Poisson's ratio of −0.85. A hinge‐like honeycomb network in the spinel structure is identified as being responsible for the negative Poisson's ratio. This phenomenon has a substantial effect on the functional properties of CoFe2O4 and enables the construction of a new class of nano‐devices.

The electrocaloric effect in a 0.92Pb͑Zn 1/3 Nb 2/3 ͒O 3 -0.08PbTiO 3 single crystal was measured by a direct calorimetric technique as a function of sample temperature and electric field. The temperature of the maximum electrocaloric effect was found to coincide with the ferroelectric transition temperature. We present a theoretical description based on mean-field theory that gives a satisfactory description of the temperature and electric field dependence of the experimentally observed electrocaloric effect.