•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.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
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.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The metamagnetic transition in cerium-based intermetallics is a very common intriguing phenomenon that has remained the subject of close study for several decades. We report crystal structure, ...magnetization and resistivity of a new ternary cerium germanide Ce3Pd2Ge7 with an orthorhombic structure of La3Co2Sn7-type (space group Cmmm, cell dimensions a = 4.3257(3), b = 26.339(2), c = 4.3594(3) Å, V = 496.69(2) Å3). Low-temperature magnetic properties are characterized by a two-step metamagnetic transition, which can be associated with two nonequivalent positions of Ce ions in the lattice. The first metamagnetic transition occurs in weak magnetic fields below T1 ≈ 11 K and then moves to higher fields when the temperature goes down (B ∼ 1.5 T at T = 2 K). The second transition manifests itself below T2 ≈ 8 K as a rapid increase of magnetization, which starts from zero field and reaches saturation at fields B ≈ 0.1 T. The magnitude of each transition increases with decreasing temperature and the polarized magnetization ΔM reaches 0.13 μB/Ce and 0.08 μB/Ce upon the first and second transitions respectively. The interchange of nonmagnetic Pd and Ge ions (≈ 0.8 %) leads to the appearance of a hysteresis of metamagnetic transitions, as well as to the splitting of the field cooled (FC) and zero field cooled (ZFC) magnetization curves in hysteresis area. The dependence of the polarized magnetization ΔM on temperature which persists up to high fields as well as the continuation of the hysteresis well above the metamagnetic transition (at least up to B ∼ 9 T) indicates a new type of spin-glass-like state, which is caused by the suppression of spin fluctuations and the localization of magnetic moments during the metamagnetic transition.
•-Synthesis and crystal structure analysis of a new ternary cerium intermetallide.•-Magnetic properties are caused by metamagnetic transitions on nonequivalent Ce ions.•-Metamagnetic transition is caused by suppression of Kondo spin fluctuations.•-Non-magnetic atomic disorder causes spin-glass state with hysteresis behavior.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
Influence of Co addition on magnetic, transport properties and electron structure of Ni50−xCoxMn31+yAl19−y (x = 0-10, y = 0-3) Heusler alloys were investigated experimentally and theoretically by ...first-principles calculations in the framework of density functional theory with an account of supercell approach. Cobalt doping from 0 to 10 at. % was found to increase the martensitic transition temperature T0 = (Ms + Af)/2 from 280 to 365.5 K. Magnetization of austenite phase sharply increases and magnetic order changes from antiferromagnetic to ferromagnetic state, while in martensite phase magnetization slightly growing with cobalt content. From theoretical point of view, Co-doping leads to formation of additional exchange interactions between magnetic moments of Co-Mn and Ni-Co atoms, which leads to ferromagnetism in austenite. Theoretical calculations show that from 4.68 at. % of Co content ferromagnetic order is preferred. Martensitic transformation is suppressed in alloys with more than 9.5 at. % of cobalt. It was supported by theoretical calculations of the energy difference between austenite and martensite states as a function of cobalt content. We show that the energy difference between austenite and martensite phases in L21 structure from x ≥ 6.25 at. % of Co became negative, what points on the absence of martensitic transformation. For B2 structure, the energy difference is positive for all concentrations of cobalt, that proves that phase transition is likely to occur.
•The martensitic transformation is suppressed by Co content higher than 9.5 at.%.•An addition of Co results in an enhancement of ferromagnetism.•Contrary, for the L21 ordered Ni-(Co)-Mn-Al, the martensitic phase becomes unstable.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Abstract
Introducing of topological insulator concept for fluctuating valence compound – samarium hexaboride – has recently initiated a new round of studies aimed to clarify the nature of the ground ...state in this extraordinary system with strong electron correlations. Here we discuss the data of magnetic resonance in the pristine single crystals of SmB
6
measured in 60 GHz cavity experiments at temperatures 1.8–300 K. The microwave study as well as the DC resistivity and Hall effect measurements performed for the different states of SmB
6
110 surface prove definitely the existence of the layer with metallic conductivity increasing under lowering temperature below 5 K. Four lines with the g-factors g ≈ 2 are found to contribute to the ESR-like absorption spectrum that may be attributed to intrinsic paramagnetic centers on the sample’s surface, which are robust with respect to the surface treatment. The temperature dependence of integrated intensity
I
(
T
) for main paramagnetic signal is found to demonstrate anomalous critical behavior
I
(
T
) ~ (
T
*
−
T
)
ν
with characteristic temperature
T
*
= 5.34 ± 0.05 K and exponent ν = 0.38 ± 0.03 indicating possible magnetic transition at the SmB
6
110 surface. Additional resonant magnetoabsorption line, which may be associated with either donor-like defects or cyclotron resonance mode corresponding to the mass
m
c
~ 1.2
m
0
, is reported.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Detailed measurements of the Hall effect in the paramagnetic phase of Ho
0.8
Lu
0.2
B
12
antiferromagnet at the magnetic field up to 80 kOe in the temperature range of 1.9–300 K have been performed. ...It has been found that the transition to the cage glass phase (
T
<
T
* ~ 60 K) is accompanied by the appearance of a positive Hall resistance component in addition to that corresponding to the negative Hall effect. The amplitude and angular dependence of the former depend on the magnitude and direction of the applied magnetic field with respect to the crystallographic axes. The revealed anisotropy of the Hall effect in Ho
0.8
Lu
0.2
B
12
is attributed to the interaction of charge carriers with dynamic charge stripes.
Full text
Available for:
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
PDF
