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Updated: Jul 27, 2025

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope
Published on: March 24, 2019
Spin-liquid state with precursor ferromagnetic clusters interacting antiferromagnetically in frustrated glassy
S K Jena1, M S Seehra2, T Sarkar3
1Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India.
Abstract:
Spinels (AB2O4) with magnetic ions occupying only the octahedralBsites 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 (Zn0.82+Cu0.22+)A[Fe0.42+Fe0.63+Mn3+]BO4‒δ. Analysis of the temperature dependence of magnetization (M), ac magnetic susceptibilities (χ'andχ''), dc susceptibility (χ), heat capacityCp, and neutron diffraction (ND) measurements show complex temperature-dependent short-range order (SRO) but without LRO. The data ofχ vs. Tfits the Curie-Weiss law:χ = C/(T ‒ θ) fromT= 250 K to 400 K withθ≃ 185 K signifying dominant ferromagnetic (FM) coupling with the FM exchange constantJ/kB= 17 K, andC= 3.29 emu K mol‒1Oe‒1yielding an effective magnetic momentµeff= 5.13µBresulting from the high-spin states of Cu2+(Asite) and Fe2+(Bsite), while theBsite trivalent ions Mn3+and Fe3+are in their low-spin states. The extrapolated saturation magnetization obtained from theM vs. Hdata atT= 2 K is explained using the spin arrangement (Cu2+↓)A[Fe2+↑, Fe3+↓, Mn3+↑]Bleading to FM clusters interact antiferromagnetically at low temperatures. Temperature dependence of d(χT)/dTshows the onset of ferrimagnetism below ∼100 K and peaks near 47 K and 24 K. The relaxation timeτobtained from temperature and frequency dependence ofχ″when fit to the power law and Vogel-Fulcher laws confirm the cluster spin-glass (SG) state. The magnetic field dependence of the SG temperatureTSGHfollows the equation:TSGH=TSG01-AH2/ϕwithTSG(0) = 46.6 K,A= 8.6 × 10‒3Oe‒0.593andϕ= 3.37. The temperature dependence of hysteresis loops yields coercivityHC∼ 3.8 kOe at 2 K without exchange-bias, butHCdecreases with increase inTbecoming zero above 24 K, theTSG(H) forH= 800 Oe. Variations ofCpvs. Tfrom 2 K to 200 K inH=0 andH=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. ForT< 9 K,Cpvaries asT2; 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 magnetizationMTRM(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 atTSG(0) = 46.6 K, followed by SL behavior below 9 K.
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