Magnetic control of large room-temperature polarization

Kumar, Ashok and Sharma, G L and Katiyar, R S and Pirc, R and Blinc, R and Scott, J F. (2009) Magnetic control of large room-temperature polarization. Journal of Physics: Condensed Matter, 21 (38). p. 382204. ISSN 0953-8984

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Numerous authors have referred to room-temperature magnetic switching of large electric polarizations as 'the Holy Grail' of magnetoelectricity. We report this long-sought effect, obtained using a new physical process of coupling between magnetic and ferroelectric nanoregions. Solid state solutions of PFW [Pb(Fe2/3W1/3)O-3] and PZT [Pb(Zr0.53Ti0.47)O-3] exhibit some bi-relaxor qualities, with both ferroelectric relaxor characteristics and magnetic relaxor phenomena. Near 20% PFW the ferroelectric relaxor state is nearly unstable at room temperature against long-range ferroelectricity. Here we report magnetic switching between the normal ferroelectric state and a magnetically quenched ferroelectric state that resembles relaxors. This gives both a new room-temperature, single-phase, multiferroic magnetoelectric, (PbFe0.67W0.33O3)(0.2)(PbZr0.53Ti0.47O3)(0.8) ('0.2PFW/0.8PZT'), with polarization, loss (<1%), and resistivity (typically 10(8) - 10(9) Omega cm) equal to or superior to those of BiFeO3, and also a new and very large magnetoelectric effect: switching not from + P-r to - P-r with applied H, but from P-r to zero with applied H of less than a tesla. This switching of the polarization occurs not because of a conventional magnetically induced phase transition, but because of dynamic effects: increasing H lengthens the relaxation time by 500 x from <200 ns to >100 mu s, and it strongly couples the polarization relaxation and spin relaxations. The diverging polarization relaxation time accurately fits a modified Vogel-Fulcher equation in which the freezing temperature T-f is replaced by a critical freezing field H-f that is 0.92 +/- 0.07 T. This field dependence and the critical field H-c are derived analytically from the spherical random bond random field model with no adjustable parameters and an (EH2)-H-2 coupling. This device permits three-state logic (+P-r, 0,-P-r) and a condenser with >5000% magnetic field change in its capacitance; for H = 0 the coercive voltage is 1.4 V across 300 nm for + P-r to -P-r switching, and the coercive magnetic field is 0.5 T for + P-r to zero switching.

Item Type: Article
InterNano Taxonomy: Nanoscale Objects and Nanostructured Materials > Nanocomposites > Thin films
Nanomanufacturing Characterization Techniques > Magnetic Characterization
Collections: Nanomanufacturing Research Collection
Depositing User: Moureen Kemei
Date Deposited: 22 Feb 2010 22:56
Last Modified: 22 Feb 2010 22:56

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