From quasi-two-dimensional metal with ferromagnetic bilayers to Mott insulator with G-type antiferromagnetic order in Ca<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>3</mml:mn></mml:msub></mml:math>(Ru<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:math>Ti<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"

Jin, Peng; Ke, Xianglin; Wang, Gaochao; Ortmann, J. Elliott; Fobes, David; Hong, Tao; Wu, Xiaoshan; Mao, Zhiqiang

doi:10.1103/physrevb.87.085125

Cited by 23 publications

(39 citation statements)

References 31 publications

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“…The material of interest in this paper, Ca3(Ru0.97Ti0.03)2O7, shows a metallic state with the AFM-a type magnetic order for TMIT (~46 K) < T < TN (~62 K) but a Mott insulating state with the G-AFM order for T < TMIT. According to the T-x phase diagram of Ca3(Ru1-xTix)2O7 ( Figure S1 [24]), Ca3(Ru0.97Ti0.03)2O7 sits right at the boundary between the correlated metallic phase and the Mott insulating phase [23], and the physical properties and responses to external stimuli are to a great extent determined by the competition between these two distinct magnetic and electronic instabilities. Thus, it serves as a model system to explore exotic phenomena of strongly correlated electrons in the vicinity of the MIT.…”

Section: Chinamentioning

confidence: 99%

Colossal Magnetoresistance in a Mott Insulator via Magnetic Field-Driven Insulator-Metal Transition

et al. 2016

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We present a new type of colossal magnetoresistance (CMR) arising from an anomalous collapse of the Mott insulating state via a modest magnetic field in a bilayer ruthenate, Ti-doped Ca3Ru2O7. Such an insulator-metal transition is accompanied by changes in both lattice and magnetic structures. Our findings have important implications because a magnetic field usually stabilizes the insulating ground state in a Mott-Hubbard system, thus calling for a deeper theoretical study to reexamine the magnetic field tuning of Mott systems with magnetic and electronic instabilities and spin-lattice-charge coupling. This study further provides a model approach to search for CMR systems other than manganites, such as Mott insulators in the vicinity of the boundary between competing phases.

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Section: Chinamentioning

confidence: 99%

Colossal Magnetoresistance in a Mott Insulator via Magnetic Field-Driven Insulator-Metal Transition

et al. 2016

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“…1a. Unlike our previously-reported phase diagram28 which shows the evolution of magnetic structure in a wide composition range, the current phase diagram is focused on the magnetic phase separation region near the critical Ti concentration. Our goal of establishing such a detailed phase diagram is to examine if there exists any other intermediate magnetic phases between the AFM-b and G-AFM phase.…”

Section: Resultsmentioning

confidence: 98%

“…Unlike manganites, Ca 3 Ru 2 O 7 features comparable energy scales between the double-exchange FM and superexchange AFM interactions. The phase coherence of those small Fermi pockets is quite easy to be destroyed by Ti impurities, which are strong scattering centers28. Once those surviving itinerant electrons are localized, FM coupling strength would be reduced very quickly so that the checkboard super-exchange coupling becomes dominate, resulting in a G-AFM state.…”

Section: Discussionmentioning

confidence: 99%

“…An intermediate magnetic (IM) phase in a narrow temperature range between AFM-a and AFM-b is found, which exhibits an incommensurate component2728. Moreover, no change in space group symmetry was detected across the MIT in the limitation of XRD and neutron measurements despite the changes in lattice parameters27.…”

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confidence: 93%

“…In the present, we explore the underlying physics of the magnetic transition discovered in Ti doped Ca 3 Ru 2 O 7 2728. Undoped Ca 3 Ru 2 O 7 shows an antiferromagnetic (AFM) transition at 56 K, which is then followed by a metal-insulator transition (MIT) at 48 K2425.…”

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Magnetic phase separation in double layer ruthenates Ca3(Ru1−xTix)2O7

Jin

Liu

et al. 2016

Sci Rep

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A phase transition from metallic AFM-b antiferromagnetic state to Mott insulating G-type antiferromagnetic (G-AFM) state was found in Ca3(Ru1−xTix)2O7 at about x = 0.03 in our previous work. In the present, we focused on the study of the magnetic transition near the critical composition through detailed magnetization measurements. There is no intermediate magnetic phases between the AFM-b and G-AFM states, which is in contrasted to manganites where a similar magnetic phase transition takes place through the presence of several intermediate magnetic phases. The AFM-b-to-G-AFM transition in Ca3(Ru1−xTix)2O7 happens through a phase separation process in the 2–5% Ti range, whereas similar magnetic transitions in manganites are tuned by 50–70% chemical substitutions. We discussed the possible origin of such an unusual magnetic transition and compared with that in manganites.

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Electron mass enhancement and magnetic phase separation near the Mott transition in double-layer ruthenates

Jin¹,

Gu²,

Zhou³

et al. 2018

Front. Phys.

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We present a detailed investigation of the specific heat in Ca3(Ru1-xMx)2O7 (M = Ti, Fe, Mn) single crystals. With different dopants and doping levels, three distinct regions are present, including a quasi-2D metallic state with an antiferromagnetic (AFM) order formed by ferromagnetic bilayers (AFM-b), a Mott insulating state with G-type AFM order (G-AFM) and a localized state with a mixed AFM-b and G-AFM phase. Our specific heat data provide deep insights into the Mott transitions induced by Ti and Mn dopings. We observed not only an anomalous large mass enhancement but also an additional term in the specific heat i.e. 2 C T in the localized region. The 2 C T  term is most likely due to the long-wavelength excitations with both FM and AFM components. A decrease of Debye temperature is observed in the G-type AFM region, indicating a lattice softening associated with the Mott transition. n  . However, non-zero value of  in insulating materials were reported before. P. W. Anderson proposed that the linear specific heat component is a general feature on the glassy state, including spin glass, due to statistical distribution of localized "tunneling levels[28]. Interestingly, various studies of manganites reveal large γ in insulating crystalline compositions. For example, in Nd0.67Sr0.33MnO3, a value of 2 25 / mJ mol K   was observed and in the electron-doped system La2.3Ca0.7Mn2O3, 2 41 / mJ mol K   .[29,30]. In the hole-doped LaMnO3+δ,  reaches as high as 2 23/ mJ mol K [31]. In La0.2Sr0.8MnO3, 2 5.6 / mJ mol K   [32] .Obviously that the finite linear specific heat coefficient not only appear in spin glass phase.In undoped Ca3Ru2O7, the small value of sommerfeld coefficient (  ~ 1.7 mJ/ Ru mol T 2 ) arising from the non-nesting fermi surface pockets survived. In Ru-site doped Ca3Ru2O7, the itinerant Ru t2g electrons may be localized due to the potential fluctuations arising from cation substitution and spin-dependent fluctuations due to local deviations from AFM-b magnetic order. If the doping concentration is fairly low, the localization length may be fairly large. Charge carriers can thus hop through a number of Ru ions, defines limited length of bilayer FM clusters. On the other hand, the electron levels although localized, are not largely spaced in energy, allowing for thermal excitations that contribute with a linear term to specific heat. From Fig. 4, we noticed that enhanced  appears simultaneously with the T 2 term. As state above, the T 2 term is due to the longwavelength excitations with both FM and AFM components in the magnetic phase separation region.The proposed scenario above is consistent with this picture.Above scenario explain the non-zero sommerfeld coefficient in insulating state. Why this coefficient is one order larger than pristine compound. Actually, enhanced  near Mott transition is ubiquitous, especially the ones with antiferromagnetism. For example, the heavy fermion compounds, the high-Tc cuprates, the Mott-Hubbard systems V2O3 and Ni(Se1-xSx)2 [8,33,34]. In V2O3 system, met...

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From quasi-two-dimensional metal with ferromagnetic bilayers to Mott insulator with G-type antiferromagnetic order in Ca3(Ru1−xTi

Cited by 23 publications

References 31 publications

Colossal Magnetoresistance in a Mott Insulator via Magnetic Field-Driven Insulator-Metal Transition

Colossal Magnetoresistance in a Mott Insulator via Magnetic Field-Driven Insulator-Metal Transition

Magnetic phase separation in double layer ruthenates Ca3(Ru1−xTix)2O7

Electron mass enhancement and magnetic phase separation near the Mott transition in double-layer ruthenates

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