Spin-lattice relaxation in paramagnetic CdMnTe

Scalbert, D.; Cernogora, J.; Guillaume, C. Benoît à la

doi:10.1016/0038-1098(88)90210-4

Cited by 69 publications

(43 citation statements)

References 12 publications

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“…This appears to be rather striking as the EMP formation involves both spin and energy relaxation. On the other hand, such a conclusion is compatible with the previous findings [10,14], showing that the time response of the Faraday effect to the high-frequency magnetic field is described by τ SS , not by τsL. In order to explain why it could be so we recall that there is no spin response to the external field for t < τsL if spin-spin interactions are of the Heisenberg form, so that the magnetic moment is a constant of motion and τ SS-1 = 0.…”

supporting

confidence: 93%

“…As shown in Fig. 2, the experimentally obtained [10,11] ]. This appears to be rather striking as the EMP formation involves both spin and energy relaxation.…”

mentioning

confidence: 51%

“…If, however, the non-scalar part of the spin-spin interactions is Strong enough, a non-zero magnetization can be formed adiabatically already at τSL > t > τss . The magnitude of the resulting magnetization Mad = X ad H* is given by the condition that for any adiabatic process the work done by the magnetic field is equal to the change of the internal energy of the spin subsystem [10,15]. This leads to Taking H* = 10 kOe and the values for the spin heat capacity c S and the isothermal magnetic susceptibility X(T) suitable for Cd0.85Mn0.15Te at 2 K [9,16] we get (X -Xad)/X = 5%, which corresponds to the increase in the spin temperature by 0.25 K.…”

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confidence: 99%

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Formation Time of Magnetic Polarons

et al. 1995

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It is shown that non-scalar spin-spin interactions rather than spinlattice coupling or spin diffusion control the dynamics of the magnetization formation visible in time-resolved luminescence and SQUID magnetometry.PACS numbers: 78.55.Et, 75.50.Rr Progress in the application of short light pulses for monitoring of dynamical processes has made it possible to trace the emerging of exciton magnetic polarons (EMP) after optical injection of carriers across the band gap in diluted magnetic semiconductors (DMS) [1][2][3][4][5][6]. In this paper we discuss mechanisms which might account for the fast dynamics of the polaron formation in DMS.Consider a carrier trapped at t = O in a localized state. Its adiabatic wave function is described by a Schródinger equation which contains: (i) kinetic energy, taken here in the one-band effective-mass approximation, (ii) potential energy that includes the localizing and confining potential, (iii) a nonlinear term HM = HM(r, t), which describes the exchange interaction with the time-dependent polarization of the surrounding localized spins, Here J = α or Q is the electron-or hole-magnetic ion exchange integral, while g and M0 (H) denote the Lande factor and the equilibrium magnetization of the localized spins, respectively. The molecular field H* produced by the carrier and experienced by the ionic spins appears at t = 0, and is then given by Finally, G(r, t) is the response function of the spins. As a starting point we assume that it can be described by Bloch equations with the diffusion term included.

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supporting

confidence: 93%

“…As shown in Fig. 2, the experimentally obtained [10,11] ]. This appears to be rather striking as the EMP formation involves both spin and energy relaxation.…”

mentioning

confidence: 51%

mentioning

confidence: 99%

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Formation Time of Magnetic Polarons

et al. 1995

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“…This model describes also the thermally-activated transitions. The long spin relaxation time of paramagnetic ions comes from the spin-lattice interaction (τ spin−lattice ∼ 1−100 ms) 20 . For the Mn relaxation rate in the absence of an exciton, we choose Γ Mn = 1/10 ms.…”

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confidence: 99%

Optical probing of the spin state of a single magnetic impurity in a self-assembled quantum dot

Govorov

2004

Phys. Rev. B

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We describe the optical resonant manipulation of a single magnetic impurity in a self-assembled quantum dot. We show that using the resonant pumping one can address and manipulate selectively individual spin states of a magnetic impurity. The mechanisms of resonant optical polarization of a single impurity in a quantum dot involve anisotropic exchange interactions and are different to those in diluted semiconductors. A Mn impurity can act as qubit. The limiting factors for the qubit manipulation are the electron-hole exchange interaction and finite temperature.The spins of electrons in semiconductors strongly couple with electric and magnetic fields due to the spin-orbit and exchange interactions. Spintronics and quantum computation utilize these interactions to manipulate the electron spins 1,2 . One important class of spintronics materials is diluted magnetic semiconductors 3 which combine high-quality semiconductor structures with magnetic properties of impurities. Since many semiconductors efficiently emit and absorb light, the spin states of electrons and magnetic impurities can be manipulated optically by using circularly-polarized light pulses 4 . In diluted magnetic semiconductors such as bulk crystals, quantum wells and dots, photo-generated excitons interact with a large collection of spins of Mn impurities and therefore a large number of degrees of freedom becomes involved 5,6,7,8,9,10,11 . In these systems, it is challenging to address individual spins of Mn atoms. At the same time, the quantum computational schemes are based on qubits, pairs of well-controlled quantum states. These elementary blocks, qubits, should be made interacting or decoupled on demand. In a diluted magnetic semiconductor, even a single Mn atom has 6 spin states (I Mn = 5/3). Therefore, 15 different pairs of states (qubits) can be defined for a single Mn impurity. Here we study a system which allows us to manipulate optically a single Mn spin. This system is composed of a quantum dot (QD) and a single Mn impurity. Note that the optical properties of a QD with a single Mn impurity were recently discussed in refs. 12,13 . This letter describes a single Mn impurity embedded into a self-assembled QD. Importantly, such a system permits efficient selective optical control and manipulation of individual spin states and defining a single qubit for the Mn impurity. This ability comes from the exciton spectrum of a QD with a Mn atom. An exciton in a QD has a well-defined discrete spectrum and, simultaneously, strongly interacts with the Mn spin via the exchange interaction. Since the exciton and Mn spin functions become strongly mixed, the resonant optical excitation strongly affect the spin state of Mn impurity. In particularly, we show that one can write spin states of Mn atom. Since spin relaxation of paramagnetic ions in the absence of carriers (i.e. after the exciton recombination) is an extremely slow process (∼ 10 µs), a single Mn spin is a very promising candidate for spintronics applications. The mechanisms of Mn-spin polarizati...

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“…5 [30], where the polaron formation rate τf-1 ^, as determined by various authors [21][22][23][24], is compared to the experimentally obtained [31,32] spin-lattice τ^Ź and the spin-spin relaxation rate τSS-1, deduced from the EPR studies [33,34]. As shown, τf deduced from time-resolved luminescence [21-23, 27, 28] and from the SQUID magnetometry [24] are of the same order.…”

Section: Bound Magnetic Polaronsmentioning

confidence: 82%

From Magnetic Polarons to Ferromagnetism

Dietl

1998

Acta Phys. Pol. A

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A brief overview is given on selected effects of the exchange coupling between effective mass electrons and localized spins in II-VI semiconductors containing Mn ions. In the case of a carrier or exciton trapped by an impurity or defect, the exchange interaction leads to zero-field spin-splitting.The current theory of such complexes, known as bound magnetic polarons, describes correctly their spectroscopic and thermodynamic properties as well as their formation dynamics. At the same time, a free magnetic polarona delocalized carrier accompanied by a traveling clond of polarized spinsis not expected to exist for the actual values of the coupling constants. However, hołe scattering by thermodynamic and static fluctuations is shown to affect significantly its energy. For a strong coupling, the corresponding renormalization has to be described by a non-perturbative approach. Finally, the influence of the carrier liquid upon the Mn spins is discussed. Here, either optical pumping or p-type doping may lead to a ferromagnetic order, both in bulk and layered structures. Because of a long-range character of the carrier mediated interactions, this ordering is not destroyed by the fluctuations, even in the reduced dimensionality systems.

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Spin-lattice relaxation in paramagnetic CdMnTe

Cited by 69 publications

References 12 publications

Formation Time of Magnetic Polarons

Formation Time of Magnetic Polarons

Optical probing of the spin state of a single magnetic impurity in a self-assembled quantum dot

From Magnetic Polarons to Ferromagnetism

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