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Spin-liquid state with precursor ferromagnetic clusters interacting antiferromagnetically in frustrated glassy tetragonal spinel Zn0.8Cu0.2FeMnO4

Jena, S. K. (författare)
Indian Inst Technol Guwahati, Dept Phys, Gauhati 781039, Assam, India.
Seehra, M. S. (författare)
West Virginia Univ, Dept Phys & Astron, Morgantown, WV 26506 USA.
Sarkar, Tapati (författare)
Uppsala universitet,Institutionen för materialvetenskap
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Reehuis, M. (författare)
Helmholtz Zentrum Berlin Mat & Energie, Hahn Meitner Pl 1, D-14109 Berlin, Germany.
Hoser, A. (författare)
Helmholtz Zentrum Berlin Mat & Energie, Hahn Meitner Pl 1, D-14109 Berlin, Germany.
Weise, B. (författare)
Leibniz IFW Dresden, Inst Complex Mat, D-01069 Dresden, Germany.
Thota, S. (författare)
Indian Inst Technol Guwahati, Dept Phys, Gauhati 781039, Assam, India.
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Indian Inst Technol Guwahati, Dept Phys, Gauhati 781039, Assam, India West Virginia Univ, Dept Phys & Astron, Morgantown, WV 26506 USA. (creator_code:org_t)
IOP Publishing, 2023
2023
Engelska.
Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 35:37
  • Tidskriftsartikel (refereegranskat)
Abstract Ämnesord
Stäng  
  • Spinels (AB(2)O(4)) with magnetic ions occupying only the octahedral B sites have inherent magnetic frustration which inhibits magnetic long-range order (LRO) but may lead to exotic states. Here we report on the magnetic properties of the tetragonal spinel Zn0.8Cu0.2FeMnO4, the tetragonality resulting from the Jahn-Teller active Mn3+ ions. X-ray diffraction and x-ray photoelectron spectroscopy of the sample yielded the composition (Zn-0.8(2+) Cu-0.2(2+)) A [Fe-0.4(2+) Fe-0.6(3+) Mn3+](B)O4-delta. Analysis of the temperature dependence of magnetization (M), ac magnetic susceptibilities (chi' and chi''), dc susceptibility (chi), heat capacity C-p, and neutron diffraction (ND) measurements show complex temperature-dependent short-range order (SRO) but without LRO. The data of chi vs. T fits the Curie-Weiss law: chi = C/(T - theta) from T = 250 K to 400 K with theta similar or equal to 185 K signifying dominant ferromagnetic (FM) coupling with the FM exchange constant J/k(B) = 17 K, and C = 3.29 emu K mol(-1) Oe(-1) yielding an effective magnetic moment mu(eff) = 5.13 mu B resulting from the high-spin states of Cu2+ (A site) and Fe2+ (B site), while the B site trivalent ions Mn3+ and Fe3+ are in their low-spin states. The extrapolated saturation magnetization obtained from the M vs. H data at T = 2 K is explained using the spin arrangement (Cu2+down arrow)(A)[Fe2+down arrow, Fe3+down arrow, Mn3+down arrow](B) leading to FM clusters interact antiferromagnetically at low temperatures. Temperature dependence of d(chi T)/ dT shows the onset of ferrimagnetism below similar to 100 K and peaks near 47 K and 24 K. The relaxation time t obtained from temperature and frequency dependence of chi'' when fit to the power law and Vogel-Fulcher laws confirm the cluster spin-glass (SG) state. The magnetic field dependence of the SG temperature T-SG (H) follows the equation: T-SG (H) = T-SG (0) [ 1- AH(2/phi)] with T-SG (0) = 46.6 K, A = 8.6 x 10(-3) Oe(-0.593) and phi = 3.37. The temperature dependence of hysteresis loops yields coercivity H-C similar to 3.8 kOe at 2 K without exchange-bias, but HC decreases with increase in T becoming zero above 24 K, the T-SG(H) for H = 800 Oe. Variations of C-p vs. T from 2 K to 200 K in H = 0 and H = 90 kOe do not show any peak characteristic of LRO. However, after correcting for the lattice contribution, a broad weak peak typically of SRO becomes evident centered around 40 K. For T < 9 K, Cp varies as T-2; a typical signature of spin-liquids (SLs). Comparison of the ND measurements at 1.7 K and 79.4 K shows absence of LRO. Time dependence of thermo-remanent magnetization MTRM(t) studies below 9 K reveal weakening of the inter-cluster interaction with increase in temperature. A summary of these results is that in Zn0.8Cu0.2FeMnO4, ferromagnetic clusters interact antiferromagnetically without LRO but producing a cluster SG state at T-SG(0) = 46.6 K, followed by SL behavior below 9 K.

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)
NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Nyckelord

spin-liquids
JahnTeller effect
spin-glass
pyrochlore

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