PbFe\(_{1/2}\)Ta\(_{1/2}\)O\(_{3}\) (PFT) belongs to the family of PbB\('_{x}\)B\("_{1-x}\)O\(_{3}\) which have inherent chemical disorder at the B-site. Due to this disorder, a complex magnetic ...phase diagram is expected in the material. In this paper, we report experimental results of magnetic properties in PFT through macroscopic characterization, neutron scattering and M\"{o}ssbauer spectroscopy techniques. With these results we show for the first time that PbFe\(_{1/2}\)Ta\(_{1/2}\)O\(_{3}\) behaves very similar to PbFe\(_{1/2}\)Nb\(_{1/2}\)O\(_{3}\), i.e, it undergoes AF transition at 153 K and has a spinglass transition at 10 K, below which the antiferromagnetism coexists with spinglass. We suggest that the mechanism which is responsible for such a non-trivial ground state can be explained by a speromagnet-like spin arrangement similar to the one proposed for PbFe\(_{1/2}\)Nb\(_{1/2}\)O\(_{3}\).
Inelastic neutron scattering is used to measure spin excitations in fully
deuterated single crystal samples of the strong-leg antiferromagnetic S=1/2
spin ladder compound ...(C$_7$H$_{10}$N)$_2$CuBr$_4$. Sharp resolution-limited
magnons are observed across the entire one-dimensional Brillouin zone. The
results validate the previously proposed {\it symmetric} spin ladder model and
provide a reliable estimate of the relevant exchange interactions.
The quasi one-dimensional compound BaCu2Si2O7 demonstrates numerous spin-reorientation transitions both for a magnetic field applied along the easy axis of magnetization, and for a magnetic field ...applied perpendicular to it. The magnetic phase diagram for all three principal orientations is obtained by magnetization and specific heat measurements. Values of all critical fields and low-temperature values of magnetization jumps are determined for all transitions.
We report on the experimental demonstration of a new radiation phenomenon on the nanoscale and its engineering into a reconfigurable metadevice: luminescence emission lines within the Fermi sea can ...be created by nanopatterning metal surfaces and tuned by external electrical inputs.
Fine details of the excitation spectrum of the two-dimensional spin-gap magnet PHCC are revealed by electron spin resonance investigations. The values of anisotropy parameters and the orientations of ...the anisotropy axes are determined by accurate measurements of the angular, frequency-field and temperature dependences of the resonance absorption. The properties of a spin-gap magnet in the vicinity of critical field are discussed in terms of sublevel splittings and g-factor anisotropy.
We report results of an electron spin resonance (ESR) study of a spin-gap antiferromagnet (C\(_4\)H\(_{12}\)N\(_2\))(Cu\(_2\)Cl\(_6\)) (nicknamed PHCC) with chlorine ions partially substituted by ...bromine. We found that up to 10% of nominal doping the contribution of the random defects to the absorption spectra remains at about 0.1% per copper ion, almost the same as in the pure system. Instead, a particular kind of ESR absorption corresponding to gapless S=1 triplets is observed at low temperatures in samples with high nominal bromine content x>5%. Increase of bromine concentration also leads to the systematic broadening of ESR absorption line indicating reduction of the quasi-particles lifetime.
The disordered antiferromagnet \pfn (\pfns) is investigated in a wide temperature range by combining M\"ossbauer spectroscopy and neutron diffraction experiments. It is demonstrated that the magnetic ...ground state is a {\it microscopic} coexistence of antiferromagnetic and a spin-glass orders. This speromagnet-like phase features frozen-in short-range fluctuations of the Fe\(^{3+}\) magnetic moments that are transverse to the long-range ordered antiferromagnetic spin component.
Neutron diffraction and calorimetric measurements are used to study the field-induced quantum phase transition in piperazinium-Cu\(_2\)(Cl\(_{1-x}\)Br\(_x\))\(_6\) (\(x=0\), x=3.5% and x=7.5%), a ...prototypical quantum antiferromagnet with random bonds. The critical indexes \(\phi\) and \(\beta\) are determined. The findings contradict some original predictions for Bose Glass based on the assumption \(z=d\), but are consistent with recent theoretical results implying \(z<d\). Inelastic neutron experiments reveal that disorder has a profound effect on the lowest-energy magnetic gap excitation in the system.
The spin dynamics of a quasi one dimensional \(S=1\) bond alternating spin-gap antiferromagnet Ni(C\(_9\)H\(_{24}\)N\(_4\))NO\(_2\)(ClO\(_4\)) (abbreviated as NTENP) is studied by means of electron ...spin resonance (ESR) technique. Five modes of ESR transitions are observed and identified: transitions between singlet ground state and excited triplet states, three modes of transitions between spin sublevels of collective triplet states and antiferromagnetic resonance absorption in the field-induced antiferromagnetically ordered phase. Singlet-triplet and intra-triplet modes demonstrate a doublet structure which is due to two maxima in the density of magnon states in the low-frequency range. A joint analysis of the observed spectra and other experimental results allows to test the applicability of the fermionic and bosonic models. We conclude that the fermionic approach is more appropriate for the particular case of NTENP.
