Titanium-III warwickites: A family of one-dimensional disordered magnetic systems

Fernandes, J. C.; Guimarães, R. B.; Continentino, M. A.; Borges, H. A.; Valarelli, José Vicente; Lacerda, A.

doi:10.1103/physrevb.50.16754

Cited by 53 publications

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“…In MgTiOBO 3 , evidence for a RSP-like behaviour was previously obtained from specific heat C(T ), susceptibility χ(T ) and magnetization m(H) measurements [13]. These quantities exhibit the characteristic power law behavior associated with a RSP, χ(T ) ∝ T −α , down to the lowest measured temperature.…”

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confidence: 76%

“…A previous study of a diluted magnetic material [7] has shown the importance of entanglement, but to our knowledge, this is the first experimental measurement of quantum entanglement in a magnetic material. As representative systems, we analyze the pyroborate MgMnB 2 O 5 [11,12] and the warwickite MgTiOBO 3 [13], two quasi-one dimensional disordered spin compounds with previously known magnetic and thermodynamic properties that suggest the existence of either a RSP or a Griffiths phase (GP) [14] at low temperatures.…”

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confidence: 99%

“…The more abundant impurity was the non-magnetic MgTiO 5 . More details on sample preparation were previously published [12,13]. Dc magnetization and ac susceptibility measurements were performed with a commercial apparatus (Quantum Design PPMS).…”

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Experimental observation of quantum entanglement in low-dimensional spin systems

et al. 2007

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We report macroscopic magnetic measurements carried out in order to detect and characterize field-induced quantum entanglement in low dimensional spin systems. We analyze the pyroborate MgMnB2O5 and the and the warwickite MgTiOBO3, systems with spin 5/2 and 1/2 respectively. By using the magnetic susceptibility as an entanglement witness we are able to quantify entanglement as a function of temperature and magnetic field. In addition, we experimentally distinguish for the first time a random singlet phase from a Griffiths phase. This analysis opens the possibility of a more detailed characterization of low dimensional materials.PACS numbers: 03.67. Mn, 03.67.Lx, 75.10.Pq, 75.30.Cr Since the development of quantum mechanics, entanglement has been a subject of great interest. Lately, this is mainly due to the importance of entanglement in quantum information and computation. As a consequence, a great effort has been made to detect and quantify entanglement in quantum systems [2]. In addition, quantum spin chains, a class of systems well known in solid state physics, began to be studied in the framework of quantum information theory; there are proposals for the use of such systems in quantum computation [3]. Naturally, entanglement in interacting spin chains acquired relevance in the QI community. Therefore, there has been a special effort in understanding and quantifying quantum entanglement in solid-state [1,4,5,6]. At the same time, the condensed matter community has begun to notice that entanglement may play a crucial role in the properties of different materials [7]. It is a difficult task to determine experimentally if a state is entangled or not. One of the new promising methods for entanglement detection is the use of an entanglement witnesses (EW). EW are observables which have negative expectation values for entangled states. Magnetic susceptibility was recently proposed as an EW [1] and some old experimental results were reanalyzed wthin this new framework [8].It has been known for a long time that entanglement appears in quantum spin chains, like the spin 1/2 Heisenberg model. The disordered spin 1/2 one-dimensional Heisenberg model, for example, presents a random singlet phase (RSP), where singlets of pairs of arbitrarily distant spins are formed [9]. Although entanglement was already known to exist in such chains, it had not been quantified theoretically until this decade [10]. A previous study of a diluted magnetic material [7] has shown the importance of entanglement, but to our knowledge, this is the first experimental measurement of quantum entanglement in a magnetic material. There are no experimental studies on random magnetic chains which discriminate these two phases. In this Letter, from a detailed analysis of magnetic measurements, we show unambiguously the existence of a RSP in MgTiOBO 3 , which is expected for a spin-1/2 random exchange Heisenberg antiferromagnetic chain (REHAC). In addition, our study of MgMnB 2 O 5 provides experimental evidence for the existence of a Griffiths phase ...

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Experimental observation of quantum entanglement in low-dimensional spin systems

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“…[1][2][3][4][5] These systems are mixed borates with general formula M 2ϩ M 3ϩ OBO 3 which have linear structures in the form of ribbons extending along the c axis ͑see Fig. 1͒.…”

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“…Another feature of these structures is that the cation sites are randomly occupied by the divalent and trivalent metals. 1 In MgScOBO 3 the trivalent ions Sc 3ϩ preferentially occupy (76%) the inner columns 1 and 1Ј ͑Ref. 6͒ ͑see Fig.…”

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Dimensional crossover in magnetic warwickites

et al. 1997

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We present an investigation of the magnetic properties of a series of warwickites with different transition metals. These materials are characterized by one-dimensional structures called ribbons where the transition metals are randomly located. The present results allow for a systematic investigation of the hierarchy of magnetic interactions in these systems. While the intraribbon interactions are mainly direct d-d interactions between the transition-metal ions, the interribbon interaction is due to superexchange between metals in different octahedra mediated by the oxygen in the common corner. ͓S0163-1829͑97͒00625-5͔

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Crystal and local atomic structure of MgFeBO₄ , Mg_0.5 Co_0.5 FeBO₄ and CoFeBO₄ : Effects of Co substitution

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Knyazev

et al. 2015

Phys. Status Solidi B

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Single‐crystalline MgFeBO4, Mg0.5Co0.5FeBO4, and CoFeBO4 have been grown by the flux method. The samples have been characterized by X‐ray spectral analysis, X‐ray diffraction, and X‐ray absorption spectroscopy. The X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS) spectra have been measured at the Fe and Co K‐edges over a wide temperature range (6.5–300 K). The composition, the charge state, and local environment of both Fe and Co atoms have been determined. The effects of Co substitution for Mg on the local structural distortions have been revealed experimentally and the MO bond anisotropy has been found.

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Titanium-III warwickites: A family of one-dimensional disordered magnetic systems

Cited by 53 publications

References 8 publications

Experimental observation of quantum entanglement in low-dimensional spin systems

Experimental observation of quantum entanglement in low-dimensional spin systems

Dimensional crossover in magnetic warwickites

Crystal and local atomic structure of MgFeBO₄ , Mg_0.5 Co_0.5 FeBO₄ and CoFeBO₄ : Effects of Co substitution

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Titanium-III warwickites: A family of one-dimensional disordered magnetic systems

Cited by 53 publications

References 8 publications

Experimental observation of quantum entanglement in low-dimensional spin systems

Experimental observation of quantum entanglement in low-dimensional spin systems

Dimensional crossover in magnetic warwickites

Crystal and local atomic structure of MgFeBO4 , Mg0.5 Co0.5 FeBO4 and CoFeBO4 : Effects of Co substitution

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Crystal and local atomic structure of MgFeBO₄ , Mg_0.5 Co_0.5 FeBO₄ and CoFeBO₄ : Effects of Co substitution