TY - JOUR
T1 - Quantum percolation phase transition and magneto-electric dipole glass in hexagonal ferrites
AU - Rowley, S. E.
AU - Vojta, T.
AU - Jones, A.
AU - Guo, W.
AU - Oliveira, J.
AU - Morrison, F. D.
AU - Lindfield, N.
AU - Baggio-Saitovitch, E.
AU - Watts, B. E.
AU - Scott, J. F.
N1 - SER and EBS acknowledge support from a CONFAP Newton grant. T.V. acknowledges support from the NSF under Grant No. DMR-1506152.
PY - 2017/7/17
Y1 - 2017/7/17
N2 - Hexagonal ferrites do not only have enormous commercial impact (£2 billion/year in sales) due to applications that include ultra-high density memories, credit card stripes, magnetic bar codes, small motors and low-loss microwave devices, they also have fascinating magnetic and ferroelectric quantum properties at low temperatures. Here we report the results of tuning the magnetic ordering temperature in PbFe12-xGaxO19 to zero by chemical substitution x. The phase transition boundary is found to vary as TN~(1 - x/xc)2/3 with xc very close to the calculated spin percolation threshold which we determine by Monte Carlo simulations, indicating that the zero-temperature phase transition is geometrically driven.We find that this produces a unique form of compositionally-tuned, insulating, ferrimagnetic quantum criticality. Close to the zero temperature phase transition we observe the emergence of an electric-dipole glass induced by magneto-electric coupling. The strong frequency behaviour of the glass freezing temperature Tm has a Vogel-Fulcher dependence with Tm finite, or suppressed below zero in the zero frequency limit, depending on 2 of 18 composition x. These quantum-mechanical properties, along with the multiplicity of low-lying modes near to the zero-temperature phase transition, are likely to greatly extend applications of hexaferrites into the realm of quantum and cryogenic technologies.
AB - Hexagonal ferrites do not only have enormous commercial impact (£2 billion/year in sales) due to applications that include ultra-high density memories, credit card stripes, magnetic bar codes, small motors and low-loss microwave devices, they also have fascinating magnetic and ferroelectric quantum properties at low temperatures. Here we report the results of tuning the magnetic ordering temperature in PbFe12-xGaxO19 to zero by chemical substitution x. The phase transition boundary is found to vary as TN~(1 - x/xc)2/3 with xc very close to the calculated spin percolation threshold which we determine by Monte Carlo simulations, indicating that the zero-temperature phase transition is geometrically driven.We find that this produces a unique form of compositionally-tuned, insulating, ferrimagnetic quantum criticality. Close to the zero temperature phase transition we observe the emergence of an electric-dipole glass induced by magneto-electric coupling. The strong frequency behaviour of the glass freezing temperature Tm has a Vogel-Fulcher dependence with Tm finite, or suppressed below zero in the zero frequency limit, depending on 2 of 18 composition x. These quantum-mechanical properties, along with the multiplicity of low-lying modes near to the zero-temperature phase transition, are likely to greatly extend applications of hexaferrites into the realm of quantum and cryogenic technologies.
U2 - 10.1103/PhysRevB.96.020407
DO - 10.1103/PhysRevB.96.020407
M3 - Article
SN - 1098-0121
VL - 96
JO - Physical Review. B, Condensed matter and materials physics
JF - Physical Review. B, Condensed matter and materials physics
IS - 2
M1 - 020407(R)
ER -