Modification of the magnetic-field dependence of the Peierls transition by a magnetic chain

Abstract

The magnetic-field dependence of the metal-to-insulator transition temperature, T c (B), in the quasi-onedimensional systems ͑Per͒ 2 M ͑mnt͒ 2 , with M ϭAu and Pt, was studied by magnetoresistance measurements under fields up to 18 T. In the Pt compound, our results show that T c (B) is anisotropic: T c (B) decreases as B 2 up to 18 T with a slope similar to that found in the Au compound when the magnetic field is applied parallel to the chain axis, while T c (B) decreases faster and does not follow a pure B 2 dependence when the magnetic field is applied perpendicular to the chain axis. This anisotropy of the field dependence denotes the coupling of the Peierls transition in the perylene chains to a spin-Peierls-like transition in the Pt͑mnt͒ 2 Ϫ chains, correlated with an anisotropic magnetic susceptibility, while in the Au compound a pure Peierls transition takes place. ͓S0163-1829͑96͒08445-7͔

Charge-Density Waves Survive the Pauli Paramagnetic Limit

“…This brings B P comfortably within the range of the 45 T Hybrid Magnet at the National High Magnetic Field Laboratory in Tallahassee [16,17]. Although a lower transition ( 8 K) occurs in the M = Pt salt, CDW formation there is compounded by the synchronous formation of a spin Peierls state involving localized spins on the Pt sites [16]. A pure CDW state occurs only in the case of the M = Au and Cu salts.…”

“…By contrast, pure CDW systems are free from orbital currents, yet their high condensation energies increase the demand on magnetic field strength required to reach the Pauli paramagnetic limit [4]. (Per) 2 Au(mnt) 2 is a rare example where this limit (≈ 37 T) falls within reach of the highest available quasi-static magnetic fields of 45 T [16,17]. In this paper we use temperatures down to 25 mK (roughly one-thousandth of the energy gap) to show that the CDW state surpasses the Pauli paramagnetic limit, signalling the likely appearance of an inhomogeneous phase.…”

Interaction of magnetic field-dependent Peierls and spin-Peierls ground states in(Per)2[Pt(mnt)Green1, Brooks2, Kuhns3 et al. 2011Phys. Rev. B103100View full textAdd to dashboardCite

“…This is characteristic of the generation of triplet excitations in the incommensurate (I) phase [3]. Although a non-SP model has been proposed [20], it is interesting to speculate about how a changing periodic singlet-triplet soliton configuration might affect the anomalous step-like behavior [13] Comparison of magnetic field dependent phase boundaries of (P er) 2 [P t(mnt) 2 ] determined from electrical transport and torque measurements [13,17] , 1 H NMR measurements (this work), and mean-field predictions [11] for T CDW and T SP . The 1 H NMR data represent the temperature and field where the spectra split from single to double peaks with increasing temperature (open squares) or magnetic field (open diamond).…”

“…3. For comparison, the phase boundary determined from temperature dependent electrical transport measurements [17], and magnetoresistance and torque magnetization studies [13] are also presented.…”

Spin-polarized electron tunneling between charge-density-wave metals

“…This means that for H not exceeding a certain value, mathematically analogous to the Clogston-Chandrasekhar paramagnetic limit [4], the CDW gap S( ) T may be considered as a BCS-like one, not dependent on H. Such an expectation is supported by experiment. For example, the destructive influence of H on the critical temperature, T d , of the structural phase transition was observed to be extremely small at low fields for such different substances with CDWs as the A15 compound V 3 Si [19] (T d = 20.15 K at H = 0 and is reduced by -0.6 K at H = 156 kOe) and the quasi-one-dimensional organic metal Per 2 [Au(mnt) 2 ] [20], and could not be detected for any other CDW compounds.…”