•Magnetic H-T and H-φ phase diagrams of ErB12 include a number of different AF states.•Angular MR and magnetization dependences are highly anisotropic at T < TN.•Dynamic charge stripes in RB12 play a ...key role in the formation of MR anisotropy.•Strong anisotropy in ErB12 is due to the destruction of the RKKY exchange interaction.
The nature of charge transport and magnetization anisotropy was investigated in the ErB12 antiferromagnetic metal with both cooperative Jahn-Teller distortions of the fcc crystal structure and electronic instability (dynamic charge stripes). A butterfly pattern of the H-φ magnetic phase diagram in the (1 1 0) plane was reconstructed, including a large number of different magnetic phases separated from each other by radial and circular boundaries. It is argued that fluctuations of electron density are responsible for the suppression of the indirect Ruderman-Kittel-Kasuya-Yoshida (RKKY) exchange between the nearest neighbored Er3+ ions located along the 〈110〉 directions producing the magnetic phase diversity in ErB12.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Magnetic and transport properties of Mn2FeAl were studied.•Mn2FeAl is strongly frustrated antiferromagnet with Neel temperature 40 K.•Transport properties of Mn2FeAl are typical of “bad” metals.
...Experimental studies of polycrystalline Mn2FeAl revealed that it crystallizes in a primitive cubic structure of β-Mn type (space group P4132) and is an antiferromagnet with Néel temperature TN = 40 K. The alloy exhibits temperature dependence of transport properties typical for semiconductors and has abnormally high electrical resistivity (ρ ∼ 238 μΩ·cm at room temperature). High Curie-Weiss temperature ΘCW ∼ –905 K and a large value of the frustration parameter ƒ ≈ 23 points to a strong frustration of the magnetic subsystem. These experimental findings are in contrast with reported results of first-principles calculations which predicted Mn2FeAl to be half metallic ferrimagnet crystallizing in the Heusler crystal structure.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Randomness and frustration are believed to be two crucial criteria for the formation of spin glass state. However, the spin freezing occurs in some well-ordered crystals below the related ...temperature
T
f
due to the instability of each spin state, which induces the variation of either magnetic moment value or exchange energy. Here we explore the new mechanism of the in-site originated disorder in antiferromagnets Gd
0.73
La
0.27
B
6
and GdB
6
, which is caused by the random mutual shifts of Gd
3+
spins from the centrally symmetrical positions in the regular cubic lattice. The universal scaling of ESR linewidth temperature dependencies to the power law
ΔH
(
T
) ~ ((
T
−
T
D
)
/T
D
)
α
with
α
= − 1.1 ± 0.05 in the paramagnetic phase of both compounds demonstrates the identity of the origin of magnetic randomness. In Gd
0.73
La
0.27
B
6
the resulting random spin configurations freeze at
T
f
≈ 10.5 K where the maximum of magnetization is observed. Below
T
f
the splitting of ZFC and FC magnetization curves takes place as well as the magnetic state depends on the antecedent sample history. In the case of GdB
6
the coherent displacement of Gd ions compete with these random shifts forming an antiferromagnetic (AFM) phase at
T
N
= 15.5 K, which prevails over the spin freezing at
T
f
≈ 13 K, expected from the ESR data. The observation of the hysteresis of the ESR spectrum in the AFM phase suggests that its properties may be determined by the competition of two types of AFM orders, which results in formation of stable magnetic domains with nonequivalent positions of AFM Gd pairs at
T
< 10 K.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Accurate low temperature charge transport measurements in combination with high-precision x-ray diffraction experiments have allowed detection of the symmetry lowering in the single domain ...Tm0.19Yb0.81B12 crystals that belong to the family of dodecaborides with metal-insulator transition. Based on the fine structure analysis we discover the formation of dynamic charge stripes within the semiconducting matrix of Tm0.19Yb0.81B12. The charge dynamics in these conducting nano-size channels is characterized by broad-band optical spectroscopy that allowed estimating the frequency (~2.4 × 1011 Hz) of quantum motion of the charge carriers. It is suggested that cooperative Jahn-Teller effect in the boron sublattice is a cause of the large-amplitude rattling modes of the Tm and Yb ions responsible for the 'modulation' of the conduction band along one of the directions through the variation of 5d-2p hybridization of electron states.
Detailed measurements of the Hall effect in the Ho
0.8
Lu
0.2
B
12
antiferromagnetic compound (Néel temperature
T
N
= 5.75 K) in magnetic fields up to 80 kOe oriented in the (110) plane at ...temperatures of 1.9–6.6 K are performed. It is established with the contribution separation procedure that the anisotropic positive contribution, which is responsible for the double inversion of the sign of the Hall resistance, dominates in the antiferromagnetic state of Ho
0.8
Lu
0.2
B
12
in fields of 30–50 kOe. A sharp decrease in the amplitude of the isotropic negative contribution at the transition to the antiferromagnetic phase is found. The nature of the detected anomalies in the antiferromagnetic metal with dynamic charge stripes and spin-wave component of the magnetic structure is discussed.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The spatial spin modulated structure (SSMS) of the cycloid type present in bulk BiFeO3 prevents the linear magnetoelectric effect. One way to influence this structure is to reduce the crystal size to ...the nanoscale. Various opinions are circulating in the literature about the effect of nanocrystal size on SSMS, and to investigate this issue, we used a number of methods, with zero-field NMR (ZF NMR) spectroscopy at the forefront. ZF NMR spectroscopy enables the direct observation of the distribution profile of local fields on iron atoms and defines the SSMS presence and its properties. We also examined the synthesized samples using XRD, TEM, and magnetometry. We conclude that SSMS persists as the nanocrystal size decreases to the cycloid period and less, becoming more harmonic. This is accompanied by the change of the anisotropy type from an “easy axis” to an “easy plane”. Magnetic measurements show a significant increase in the saturation magnetization, remanent magnetization, coercivity, and exchange bias of nanocrystals with sizes close to the cycloid period, which is probably associated with incomplete spin compensation in the case of an incomplete cycloid period. Despite the fact that SSMS is retained in the samples with decreased size, the magnetic properties experience a sharp increase up to applicable values.
Optical ceramics based on Yb2O3–Y2O3-Sc2O3–Al2O3 solid solutions with a garnet structure were obtained using chemical precipitation and vacuum sintering techniques. In the samples' composition, ...scandium was incorporated into both dodecahedral and octahedral garnet sites in ratios from 4 : 1 to 1 : 4. The differential thermal analysis and dilatometry methods were used to study the phase transformations kinetics of the precursor powders and the vacuum sintering kinetics of YSAG:Yb compacts. It was found that the garnet cationic composition has a strong effect on the optical ceramics' sintering temperature ranges. It was also pointed out that an increase in the scandium content in the dodecahedral YSAG:Yb garnet site was accompanied by a decrease in the vacuum sintering temperature, which ensures maximum compaction rate. For the samples with the Y2.15Yb0.25Sc1.00Al4.6O12, Y2.35Yb0.25Sc1.00Al4.4O12, Y2.55Yb0.25Sc1.00Al4.2O12, Y2.52Yb0.25Sc0.38Al4.85O12 compositions, optical transmission in visible and near-infrared range of more than 80% was achieved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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