ABSTRACT We have made NMR and magnetization measurements on a single crystal to investigate local... more ABSTRACT We have made NMR and magnetization measurements on a single crystal to investigate local magnetic properties of an antiferromagnet metal NaV2O4 with a frustrated double-chain structure. In the paramagnetic phase, we find there is a double exchange ferromagnetic interaction, which competes with a superexchange antiferromagnetic interaction, yielding a magnetic frustration. In the magnetically ordered state, we propose an incommensurate helical structure with the bc helical plane, which appears due to the competition between the magnetic interactions, as a spin structure. Thus we conclude that the magnetic frustration closely related to a multi-band effect plays an essential role for the magnetic properties of NaV2O4.
ABSTRACT The lamellar antiferromagnet CuCr1−xInxP2S6 (TN ≈ 32 K) rapidly loses magnetic percolati... more ABSTRACT The lamellar antiferromagnet CuCr1−xInxP2S6 (TN ≈ 32 K) rapidly loses magnetic percolation upon diamagnetically diluting the triangular Cu-Cr-P2 planar network with In3+ ions. For 0 ≤ x < 0.3 anti-ferroelectricity (Tc ≤ 150 K) and antiferromagnetic spin order (TN ≤ 32 K) coexist. Both orders are superposed by ferroic fluctuations. Dynamic polar clustering with glasslike polydispersive dielectric susceptibility emerges for x > 0 at T ≤ Tc, while for x < 0.3 pseudocritical planar 2D ferromagnetic fluctuations are encountered. They give rise to Langevin-type magnetization saturation and large quasimolecular magnetic anisotropy. Third-order magnetoelectric coupling is observed in collinear field configuration.
... In disordered perovskite relaxors, such as PMN and 9/65/35 PLZT ceramics, in zero electric fi... more ... In disordered perovskite relaxors, such as PMN and 9/65/35 PLZT ceramics, in zero electric field no long-range ferroelectric state is established and relaxors undergo a freezing transition into the nonergodic pha~e[~*~I. However, by cooling ...
ABSTRACT This chapter introduces the structural background of the appearance of polar nanoregions... more ABSTRACT This chapter introduces the structural background of the appearance of polar nanoregions in relaxors, describes their major macroscopic dielectric and ferroelectric properties, and presents the results of recent investigations of local polar structures by piezoresponse force microscopy (PFM). Statistical analysis of observed nanodomains, their temperature evolution, and polarization switching results are given for several relaxor families based on Sr x Ba1–x Nb2O6 (SBN), PbMg1/3Nb2/3O3 (PMN), PbZn1/3Nb2/3O3 (PZN), and (Pb1–x La x )(Zr1–y Ti y )O3 (PLZT). The PFM technique has proved to be a powerful tool for the investigation of local properties of relaxors where optical techniques obviously fail because of their lack of resolution. In addition, size- and grain boundary-dependent phenomena in relaxors are reviewed for representative PLZT compositions. Examples of investigations of polar structures in relaxor films and ceramics and single are also presented.
ABSTRACT We have made NMR and magnetization measurements on a single crystal to investigate local... more ABSTRACT We have made NMR and magnetization measurements on a single crystal to investigate local magnetic properties of an antiferromagnet metal NaV2O4 with a frustrated double-chain structure. In the paramagnetic phase, we find there is a double exchange ferromagnetic interaction, which competes with a superexchange antiferromagnetic interaction, yielding a magnetic frustration. In the magnetically ordered state, we propose an incommensurate helical structure with the bc helical plane, which appears due to the competition between the magnetic interactions, as a spin structure. Thus we conclude that the magnetic frustration closely related to a multi-band effect plays an essential role for the magnetic properties of NaV2O4.
ABSTRACT The lamellar antiferromagnet CuCr1−xInxP2S6 (TN ≈ 32 K) rapidly loses magnetic percolati... more ABSTRACT The lamellar antiferromagnet CuCr1−xInxP2S6 (TN ≈ 32 K) rapidly loses magnetic percolation upon diamagnetically diluting the triangular Cu-Cr-P2 planar network with In3+ ions. For 0 ≤ x < 0.3 anti-ferroelectricity (Tc ≤ 150 K) and antiferromagnetic spin order (TN ≤ 32 K) coexist. Both orders are superposed by ferroic fluctuations. Dynamic polar clustering with glasslike polydispersive dielectric susceptibility emerges for x > 0 at T ≤ Tc, while for x < 0.3 pseudocritical planar 2D ferromagnetic fluctuations are encountered. They give rise to Langevin-type magnetization saturation and large quasimolecular magnetic anisotropy. Third-order magnetoelectric coupling is observed in collinear field configuration.
... In disordered perovskite relaxors, such as PMN and 9/65/35 PLZT ceramics, in zero electric fi... more ... In disordered perovskite relaxors, such as PMN and 9/65/35 PLZT ceramics, in zero electric field no long-range ferroelectric state is established and relaxors undergo a freezing transition into the nonergodic pha~e[~*~I. However, by cooling ...
ABSTRACT This chapter introduces the structural background of the appearance of polar nanoregions... more ABSTRACT This chapter introduces the structural background of the appearance of polar nanoregions in relaxors, describes their major macroscopic dielectric and ferroelectric properties, and presents the results of recent investigations of local polar structures by piezoresponse force microscopy (PFM). Statistical analysis of observed nanodomains, their temperature evolution, and polarization switching results are given for several relaxor families based on Sr x Ba1–x Nb2O6 (SBN), PbMg1/3Nb2/3O3 (PMN), PbZn1/3Nb2/3O3 (PZN), and (Pb1–x La x )(Zr1–y Ti y )O3 (PLZT). The PFM technique has proved to be a powerful tool for the investigation of local properties of relaxors where optical techniques obviously fail because of their lack of resolution. In addition, size- and grain boundary-dependent phenomena in relaxors are reviewed for representative PLZT compositions. Examples of investigations of polar structures in relaxor films and ceramics and single are also presented.
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