Single-Chain Magnets and Related Systems

Abstract

International audienceIn this chapter, the static and dynamic magnetic properties of singlechain magnets and related systems are reviewed. We will particularly focus on the so-called Ising limit for which the magnetic anisotropy energy is much larger than the energy of the intrachain exchange interactions. The simple regular chain of ferromagnetically coupled spins will be first described. Static properties will be summarized to introduce the dominant role of domain walls at low temperature. The slow relaxation of the magnetization will be then discussed using a stochastic description. The deduced dynamic critical behavior will be analyzed in detail to explain the observed magnet behavior. In particular, the effect of applying a magnetic field, often ignored in the literature, will be discussed. Then, more complicated structures including chains of antiferromagnetically coupled magnetic sites will be discussed. Finally, the importance of interchain couplings will be introduced to discriminate between a “real” single-chain magnet and a sample presenting both a magnet-type property and a three-dimensional antiferromagnetic ordered state at low temperature

An Ising iron(ii) chain exhibits a large finite-size energy barrier and “hard” magnetic behaviour

“…In addition to the linear fitting method, Δ ξ can be also deduced from the exchange parameter by Δ ξ = 2JS 2 . 7 Based on the above estimation of J from Fisher model, 2JS 2 is about 67.9 K, which agrees well to the fitting result. To verify SCM behavior of 1, alternating-current (ac) magnetic susceptibility measurements were conducted in the frequency range 0.3−1500 Hz (Fig.…”

“…6 For SCMs, the energy barrier for spin reversal (Δτ) depends not only on the anisotropic barrier for spin reversal (Δ A ) but also on the energy for domain wall creation (Δ ξ ), defined by Δτ = 2Δ ξ + Δ A (infinite chain regime) and Δτ' = Δ ξ + Δ A (finite-size chain regime). 7 Within the Ising limit, Δ A is equal to │D│S 2 (D is the zero-field splitting parameter of the spin units) and Δ ξ is equal to 2│J│S 2 (based on the Hamiltonian 7 where J is the intrachain magnetic coupling constant). It can be deduced that all the D, S and J should be maximized for larger Δτ.…”

Order in disorder: solution and solid-state studies of [MIII2MII5] wheels (MIII = Cr, Al; MII = Ni, Zn)

“…5 In the latter, heterometallic species have been employed to deliberately control exchange interactions in cyanide-bridged Prussian blue analogues, 6 obtain enhanced magnetocaloric effects in cryogenic coolers, 7 enforce spin frustration effects in high symmetry cages, 8 understand the origins of the slow relaxation dynamics in single-molecule magnets (SMMs) 9 and single-chain magnets (SCMs), 10 and for the development of molecules that may act as quantum bits (qubits). 11 A prominent, thoroughly investigated example of the latter is the large family of compounds based on [Cr III 7 Ni II ] rings.…”

Magnetic tetrastability in a spin chain

“…Using numerical and analytical calculations, we show that the so-called π/4 canted spin chain presents four stable magnetic domains with orthogonal magnetizations. Finally we show that domain walls, which are responsible for the relaxation of the magnetization (loss of information), have a finite energy which should avoid their nucleation at low temperature and therefore preserve the encoded information.Among the variety of low dimensionnal magnets, single chain magnets (SCMs) [7,8], have been extensively studied as they present a slow relaxation of magnetization, promising for information storage [7][8][9][10]. SCMs are generally made by assembling together single-molecule magnets that owns a strong uni-axial anisotropy [11].…”

“…Among the variety of low dimensionnal magnets, single chain magnets (SCMs) [7,8], have been extensively studied as they present a slow relaxation of magnetization, promising for information storage [7][8][9][10]. SCMs are generally made by assembling together single-molecule magnets that owns a strong uni-axial anisotropy [11].…”