Effects of high pressure, magnetic fields, and substitutions - ICMR ...

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FE polarization induced by exchange striction of frustrated spins Two frustrated spins tend to separate to reduce magnetic exchange energy Applies to: E-type (↑↑↓↓) magnetic order due to competing NN and NNN interactions If the associated ions have different charges => local polarization of the lattice Can add up to macroscopic polarization and ferroelectricity No need of non-collinear spin order Cheong/Mostovoy, Nature Mat. 2007 Examples: Ising chain magnet Ca 3 CoMnO 6 (Choi et al., PRL 2008) RMn 2 O 5 (R = rare earth, Y, Bi) but not RMnO 3 with E-type magnetic order (HoMnO 3 ) - no charge order
Ferroelectricity due to possible exchange striction effects in RMn 2 O 5 Magnetic structure from neutron scattering Superexchange interactions determine exchange parameters between Mn spins Mn 4+ At least 5 different exchange integrals can be distinguished ⇒ Mostly AFM Mn 3+ Ionic displacements relax the magnetic frustration and generate the polarization along the b axis c b a P
Page 1 and 2: Tuning multiferroics under extreme
Page 3 and 4: 1. Short introduction: Multiferroic
Page 5 and 6: 2. Frustration due to competing int
Page 7 and 8: Novel physical effects in multiferr
Page 9 and 10: 2. Helical magnetic order, exchange
Page 11 and 12: WMnO 4 Frustration due to competing
Page 13: Symmetry and Landau theory (Kenzelm
Page 17 and 18: 2. Magnetoelastic effects and spin-
Page 20 and 21: Structural distortions in multiferr
Page 22 and 23: Dielectric Anomaly at and below T N
Page 24 and 25: Strong spin-spin and spin-lattice c
Page 26 and 27: Search for structural anomalies at
Page 28 and 29: 3. The effects of high pressure on
Page 30 and 31: Be-Cu cap with wires, sample, and p
Page 32 and 33: Pressure - temperature phase diagra
Page 34 and 35: Pressure effects on magnetic struct
Page 36 and 37: Control of magnetic order (commensu
Page 38 and 39: Complex p - T phase diagram of DyMn
Page 40 and 41: In multiferroics with a paraelectri
Page 42 and 43: Understanding the pressure effects
Page 44 and 45: Chapon et al. (PRL 2006) explained
Page 46 and 47: Example 1: WMnO 4 In MnWO 4 the Mn
Page 48 and 49: Example 2: CuFeO 2 T. Kimura et al.

Effects of high pressure, magnetic fields, and substitutions - ICMR ...

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