Field tuning of thermally activated magnetic quantum tunnelling in Mn
                    <sub>12</sub>
                    − Ac molecules

Hernández, J. M.; Zhang, X. X.; Luìs, Fernando; Bartolomé, J.; Tejada, J.; Ziolo, Ronald F.

doi:10.1209/epl/i1996-00570-7

Cited by 291 publications

(247 citation statements)

References 14 publications

Supporting

Mentioning

230

Contrasting

Order By: Relevance

“…Very recent dynamic hysteresis and magnetization relaxation dc and ac experiments demonstrate the existence of resonant tunneling between these quantized levels in the macroscopically distinct anisotropy wells. [3][4][5][6][7][8] Theoretical studies [9][10][11][12][13] agree with experimental results. It has also been theoretically calculated 9 and experimentally tested 14 that resonant spin tunneling between the levels in the two wells is greatly enhanced by increasing the transversal component of the magnetic field, the latter due to the increased degree of mixing between the unperturbed energy levels.…”

Section: Introductionsupporting

confidence: 75%

“…13 The value of bϭ9 K suggests that tunneling occurs from m b ϭ4 for the two first resonances observed experimentally at Hϭ0.4 and 0.8 T, as has been previously reported. [3][4][5]10 Our fitting reproduces well the shape, the width, and the position of the peaks. The position of the peaks remains constant as they are due to quantum relaxation.…”

Section: Theory and Discussionsupporting

confidence: 58%

“…Both processes are governed by Boltzmann's characteristic time ϰexp⑀/T, where ⑀ 1 is 12 K, which is the energy gap between the lowest-lying levels. The levels involved in the second process are those at the top of the barrier [3][4][5][6][7] and therefore ⑀ 2 is about 40 K. The great difference in the values of the characteristic time of the two processes allows us to assume that the time dependence is mostly determined by the tunneling process. The former process considers two separated potential wells with an infinite barrier whose temperature has increased from T to T ϩ⌬T, so that we have a local thermalization of the levels in each well.…”

Section: Theory and Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Time-dependent heat capacity ofMn12clusters

et al. 1999

View full text Add to dashboard Cite

In this paper we discuss both theoretical and experimental results on the time dependence of the heat capacity of oriented Mn 12 magnetic clusters when a magnetic field is applied along their easy axis. Our calculations are based on the existence of two contributions. The first one is associated with the thermal populations of the 21 different S z levels in the two potential wells of the magnetic uniaxial anisotropy and the second one is related to the transitions between the S z levels. We compare our theoretical predictions with experimental data on the heat capacity for different resolution times at different fields and temperatures.

show abstract

Section: Introductionsupporting

confidence: 75%

Section: Theory and Discussionsupporting

confidence: 58%

Section: Theory and Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Time-dependent heat capacity ofMn12clusters

et al. 1999

View full text Add to dashboard Cite

show abstract

“…9 Quantum mechanically, spin reversal can take place by thermal activation or tunneling ͑or a combination of both͒. [10][11][12][13][14][15][16] Tunneling may occur from one side of the barrier to the other ͑Fig. 1͒ between resonant, equal-energy states "coupled" by transverse fields ͑or high-order anisotropy terms͒.…”

Section: Introductionmentioning

confidence: 99%

Longitudinal relaxation and thermoactivation of quantum superparamagnets

Zueco

García‐Palacios

2006

Phys. Rev. B

View full text Add to dashboard Cite

The relaxation mechanisms of a quantum nanomagnet are discussed in the framework of linear response theory. We use a spin Hamiltonian with a uniaxial potential barrier plus a Zeeman term. The spin, having arbitrary S, is coupled to a bosonic environment ͑phonons͒. From the eigenstructure of the relaxation matrix, we identify two main mechanisms: namely, thermal activation over the barrier, with a time scale ⌳ 1 −1 , and a faster dynamics inside the potential wells, with characteristic time ⌳ w −1 . This permits to introduce a simple analytical formula for the response, which agrees well with exact numerical results and covers experiments even under moderate to strong fields in the superparamagnetic range. In passing, we generalize known classical results for a number of quantities ͑e.g., integral relaxation times, initial decay time, Kramers' rate͒, results that are recovered in the limit S → ϱ.

show abstract

“…[9][10][11][12] These steps are characteristic of the resonant tunneling of the magnetization. 4 Furthermore the resonant tunneling may be thermally assisted.…”

Section: Introductionmentioning

confidence: 99%

Theory of quantum tunneling of the magnetization in magnetic particles

et al. 1997

View full text Add to dashboard Cite

Theory of quantum tunneling of the magnetization in magnetic particles de Raedt, Hans; Miyashita, S.; Saito, K.; García-Pablos, D.; García, N. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. We study the response of the magnetization to a time-dependent applied magnetic field H(t) in a model for a uniaxial magnet. It is shown that a staircase structure in the magnetization curve results from Landau-Zener tunneling between different pairs of nearly-degenerate energy levels. This mechanism might be relevant to the analysis of the hysteresis of nanoscale magnets at low temperatures, allowing one to extract the energy splittings from the hysteresis curve. We investigate the dependence of the staircase structure on the sweep rate dH(t)/dt, and point out some universal features of the staircase in uniaxial magnets. We also study the effect of a step-wise ͑instead of continuous͒ increase in the field, and show that the size of the steps depends sensitively on the procedure used to change the applied field. ͓S0163-1829͑97͒06042-6͔

show abstract

Field tuning of thermally activated magnetic quantum tunnelling in Mn ₁₂ − Ac molecules

Cited by 291 publications

References 14 publications

Time-dependent heat capacity ofMn12clusters

Time-dependent heat capacity ofMn12clusters

Longitudinal relaxation and thermoactivation of quantum superparamagnets

Theory of quantum tunneling of the magnetization in magnetic particles

Contact Info

Product

Resources

About

Field tuning of thermally activated magnetic quantum tunnelling in Mn 12 − Ac molecules

Cited by 291 publications

References 14 publications

Time-dependent heat capacity ofMn12clusters

Time-dependent heat capacity ofMn12clusters

Longitudinal relaxation and thermoactivation of quantum superparamagnets

Theory of quantum tunneling of the magnetization in magnetic particles

Contact Info

Product

Resources

About

Field tuning of thermally activated magnetic quantum tunnelling in Mn ₁₂ − Ac molecules