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SUMMARY:Hole Doping and Dimensionality in Geometrically Frustrated Magnets
  - Siân Dutton\, QM Group\, Cambridge
DTSTART:20120208T111500Z
DTEND:20120208T121500Z
UID:TALK36168@talks.cam.ac.uk
CONTACT:Michael Sutherland
DESCRIPTION:The extreme sensitivity in the balance of competing magnetic i
 nteractions in geometrically frustrated magnets is illustrated clearly in 
 Cr3+ spinels\, ACr2O4. Antiferromagnetic (AFM) ordering in ACr2O4 occurs a
 t a spin-Peierls transition. Both the low temperature magnetic and structu
 ral regimes are found to be highly sensitive to the A cation. In the case 
 of ZnCr2O4 we find that very fine control of the reaction conditions is ne
 cessary to make stoichiometric ZnCr2O4\, rather than hole doped Zn1+xCr2-x
 O4 (x ≤ 0.04). From analysis of magnetic measurements\, specific heat an
 d neutron diffraction we have probed the nature of the transitions at T_N.
  In light of these results how hole doping effects the low temperature pro
 perties and the role of the d2 Cr4+ cations on the isotropic d3 Cr3+ magne
 tic lattice will be discussed. The effect of hole doping in SCGO\, SrCr8Ga
 4O19\, a 2D analogue of the 3D magnetic lattice in spinels\, will also be 
 discussed.\n\nMagnetic frustration in 1D systems arises due to competition
  between the nearest neighbour\, J1 and next nearest neighbour\, J2\, inte
 ractions. Recently systems with ferromagnetic (FM) J1 and AFM J2 have rece
 ived much attention due to the complex magnetic phase diagram and the pres
 ence of a FM quantum critical point (QCP) at alpha_c = J2/J1 = -0.25. In t
 he second part of the talk a new 1D S=1/2 frustrated chain magnet\, LiCuSb
 O4 will be introduced. The proximity of LiCuSbO4 to the FM critical point 
 at alpha_c = -0.25 will be demonstrated by fitting of the thermomagnetic d
 ata to exact digitalization simulations. The absence of 3D ordering T > 10
 0 mK will be discussed in relation to the arrangement of the spin-chains w
 ithin the crystal structure.\n
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Department of Physics
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