BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Crystal and Magnetic Structures of a Family of Quantum Kagome Anti
 ferromagnets - Dr Lucy Clark\, University of Liverpool
DTSTART:20190426T133000Z
DTEND:20190426T143000Z
UID:TALK123322@talks.cam.ac.uk
CONTACT:Olivia Matthewson
DESCRIPTION:Materials constructed from kagome layers of antiferromagnetica
 lly coupled S = ½ moments are highly prized as they offer a unique opport
 unity to explore the elusive quantum spin liquid state (QSL) [1]. The mine
 ral herbertsmithite\, ZnCu3(OH)6Cl2\, for instance\, contains such an arra
 y of Cu2+ S = ½ ions and consequently\, has garnered considerable attenti
 on as a QSL candidate [2]. However\, the substantial Cu2+/Zn2+ disorder wi
 thin the crystal structure of herbertsmithite continues to call into quest
 ion our ability to rationalise its magnetic ground state [3]. More recentl
 y\, an alternative Cu2+-based mineral known as Zn-doped barlowite\, ZnCu3(
 OH)6FBr\, has shown promise as a new materialisation of the QSL state [4]\
 , with first-principles studies indicating that the extent of the anti-sit
 e disorder is reduced in comparison to herbertsmithite owing to the differ
 ent stacking of the kagome planes in Zn-barlowite [5]. Despite this intere
 st\, the crystal and magnetic structures of the parent material barlowite\
 , Cu4(OH)6FBr\, were poorly understood with several conflicting reports in
  the literature [6-8]. \nHere\, I will introduce these developments in the
  field of highly frustrated magnetism before presenting our comprehensive 
 powder neutron diffraction study of barlowite. In doing so\, I will discus
 s the intriguing structural phase transition we observe in this material a
 t T = 250 K\, and clarify the nature of its magnetic ground below TN = 15 
 K [9]. Furthermore\, I will show that we can tune the magnetic ground stat
 e of barlowite from antiferromagnetic order to quantum disorder upon Zn-do
 ping though our magnetometry and muon spectroscopy measurements. Finally\,
  I will discuss our efforts to control the nature of the structural phase 
 transition within a new family compounds through exchange of the halide io
 ns in barlowite.\n[1]	L. Savary and L. Balents\, Rep. Prog. Phys.  80\, 01
 6502 (2017).\n[2]	M. P. Shores et al.\, JACS 127\, 13462-13463 (2005).\n[3
 ]	M. Fu et al.\, Science 350\, 655-658 (2015). \n[4]	T.-H. Han\, J. Single
 ton and J. A. Schlueter\, Phys. Rev. Lett. 113\, 227203 (2014).\n[5]	Z. Lu
 i et al.\, Phys. Rev. B 92\, 220102(R) (2015).\n[6]	Z. Feng et al.\, Phys.
  Rev. B 98\, 155127 (2018).\n[7]	C. M. Pasco et al.\, Phys. Rev. Mater. 2\
 , 0444061 (2018).\n[8]	R. W. Smaha et al.\, J. Solid State Chem. 268\, 123
 -129 (2018).\n[9]	K. Tustain et al.\, Phys. Rev. Mater. 2\, 111405(R) (201
 8)\n
LOCATION: Small Lecture Theatre\, Cavendish Laboratory\, J.J. Thomson Aven
 ue
END:VEVENT
END:VCALENDAR