Spin-orbit coupling inactivity of Co2+ion in geometrically frustrated magnet GeCo2O4

Tomiyasu, Keisuke; Tominaga, A.; Hara, Shigeo; Sato, Hirohiko; Watanabe, T.; Ikeda, S.; Hiraka, Haruhiro; Iwasa, Kazuaki; Yamada, K.

doi:10.1088/1742-6596/320/1/012038

Cited by 5 publications

(4 citation statements)

References 20 publications

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“…Using μ eff = gμ B [S(S + 1)] 1/2 for μ eff = 4.6455 μ B yields g = 2.399 for spin S = 3/2 and g = 5.364 for S = 1/2. We include the possibility of S = 1/2 as the ground state of Co 2+ in ZTCO since this has been shown to be the case in several Co 2+ based system due to the combined effects of spin-orbit coupling and non-cubic crystalline field [34][35][36][37][38]. However, considering that crystalline field has cubic symmetry in ZTCO, only S = 3/2 is used in the results presented here.…”

Section: Lattice Parametermentioning

confidence: 99%

Antiferromagnetic short-range order and cluster spin-glass state in diluted spinel ZnTiCoO₄

Chowdhury¹,

Seehra²,

Pramanik³

et al. 2022

J. Phys.: Condens. Matter

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The nature of magnetism in the doubly-diluted spinel ZnTiCoO4 is reported here employing the temperature and magnetic field dependence of dc- and ac-susceptibilities, and heat capacity (CP) measurements. The antiferromagnetic Néel temperature (TN~13.8 K) is determined from the peak in the ∂(χT)/∂T vs. T plot and the Power law yields the spin-glass freezing temperature Tg ~ 12.9 K with critical exponent zν ~ 11.75. Since the magnitudes of t o and zν depend on the magnitude of Tg, a procedure is developed to find the optimum value of Tg = 12.9 K. A similar procedure is used to determine the optimum T0 = 10.9 K in the Vogel-Fulcher law yielding Ea/kB = 95 K, and t 0 = 1.6 ×10-13 sec. It is argued that the comparatively large magnitude of the Mydosh parameter Ω = 0.024 and Ea/(kBT0)=8.7(>>1) suggests cluster-spin-glass state in ZnTiCoO4 below Tg. In the CP vs T data from 1.9K to 50K, the observation of only a broad peak near 20K and absence of λ-type anomaly near TN or Tg combined with the reduced value of change in magnetic entropy from 50K to 1.9K suggests the presence of only short-range ordering in the system, consistent with spin-glass state. The field dependence of Tg shows slight departure from the non-mean-field Almeida-Thouless line. Strong temperature dependence of magnetic viscosity S and coercivity HC without exchange bias, both tending to zero on approach to Tg from below, further support the spin-glass state which results from magnetic dilution driven by Zn2+ and Ti4+ ions leading to magnetic frustration. Magnetic phase diagram in the H-T plane is established using the high-field magnetization data M(H,T) for T < TN which reveals rapid decrease of Tg with increase in H whereas decrease in TN with increase in H is weaker, typical of antiferromagnetic systems.

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Section: Lattice Parametermentioning

confidence: 99%

Antiferromagnetic short-range order and cluster spin-glass state in diluted spinel ZnTiCoO₄

Chowdhury¹,

Seehra²,

Pramanik³

et al. 2022

J. Phys.: Condens. Matter

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“…This distortion was proposed to be mainly cubic-to-tetragonal from powder neutron and X-ray diffraction [1,15]. Besides this zero-field magnetostructural behavior, a complex H-T phase diagram has been observed in GeCo 2 O 4 by magnetization, ultrasound and electron spin resonance measurements, evidencing several fieldinduced anomalies [1,9,[16][17][18][19][20][21][22]. Their microscopic origin was investigated by powder neutron diffraction under magnetic field up to 10 T [10].…”

Section: Introductionmentioning

confidence: 99%

Field-driven magnetostructural transitions in GeCo2O4

et al. 2017

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In the spinel compound GeCo2O4, the Co 2+ pyrochlore sublattice presents remarkable magnetic field-induced behaviors that we unveil through neutron and X-ray single-crystal diffraction. The Néel ordered magnetic phase is entered through a structural lowering of the cubic symmetry. In this phase, when a magnetic field is applied along a 2-fold cubic direction, a spin-flop transition of one fourth of the magnetic moments releases the magnetic frustration and triggers magnetostructural effects. At high field, these ultimately lead to an unusual spin reorientation associated with structural changes.

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“…However, an antiferromagnetic (AF) longrange order appears below T N = 21.0 K, in coincidence with a cubic-to-tetragonal structural elongation with c/a = 1.001 [7][8][9] . The AF order is composed of a dominant component described by a trigonal propagation vector Q II = (1/2, 1/2, 1/2) and an additional one described by a tetragonal Q I = (1, 0, 0)/(0, 1, 0), where the magnitude of Q I is much weaker than that of Q II 7,8,10 . GeCo 2 O 4 is a promising candidate for the frustrated system with orbital degrees of freedom 11,12 .…”

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confidence: 99%

“…Thus the metamagnetic transition at ∼1 T should occur in the Q I order which is composed of the antiferromagnetic spin chains along [110] and [1 10] directions as shown in Fig. 3(b)(i) 10 . Note that this metamagnetic transition leads to the disappearance of the Q I order, as shown in Fig.…”

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Elastic instabilities in an antiferromagnetically ordered phase of the orbitally frustrated spinel GeCo2O4

et al. 2011

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Ultrasound velocity measurements of the orbitally frustrated spinel GeCo2O4 reveal colorful and unusual elastic anomalies within the antiferromagnetic phase. Temperature dependence of shear moduli exhibits a minimum within the antiferromagnetic phase, suggesting the coupling of shear acoustic phonons to molecular spin-orbit excitations. Magnetic-field dependence of elastic moduli exhibits diplike anomalies, being interpreted as magnetic-field-induced metamagnetic and structural transitions. These elastic anomalies suggest that the survival of geometrical frustration, and the interplay of spin, orbital, and lattice degrees of freedom evoke a rich set of phenomena in the antiferromagnetic phase.

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Spin-orbit coupling inactivity of Co²⁺ion in geometrically frustrated magnet GeCo₂O₄

Cited by 5 publications

References 20 publications

Antiferromagnetic short-range order and cluster spin-glass state in diluted spinel ZnTiCoO₄

Antiferromagnetic short-range order and cluster spin-glass state in diluted spinel ZnTiCoO₄

Field-driven magnetostructural transitions in GeCo2O4

Elastic instabilities in an antiferromagnetically ordered phase of the orbitally frustrated spinel GeCo2O4

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Spin-orbit coupling inactivity of Co2+ion in geometrically frustrated magnet GeCo2O4

Cited by 5 publications

References 20 publications

Antiferromagnetic short-range order and cluster spin-glass state in diluted spinel ZnTiCoO4

Antiferromagnetic short-range order and cluster spin-glass state in diluted spinel ZnTiCoO4

Field-driven magnetostructural transitions in GeCo2O4

Elastic instabilities in an antiferromagnetically ordered phase of the orbitally frustrated spinel GeCo2O4

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Spin-orbit coupling inactivity of Co²⁺ion in geometrically frustrated magnet GeCo₂O₄

Antiferromagnetic short-range order and cluster spin-glass state in diluted spinel ZnTiCoO₄

Antiferromagnetic short-range order and cluster spin-glass state in diluted spinel ZnTiCoO₄