Modulation of slow magnetic relaxation by tuning magnetic exchange in \{Cr2Dy2\} single molecule magnets

Research output: Contribution to journalArticle

  • External authors:
  • Stuart K Langley
  • Daniel P Wielechowski
  • Veacheslav Vieru
  • Boujemaa Moubaraki
  • Liviu F Chibotaru
  • Keith S Murray

Abstract

A new series of heterometallic 3d???4f single molecule magnets ({SMMs}) of general formula [{CrIII}2DyIII2({OMe})2({RN}\{({CH}2)2OH\}2)2(acac)4({NO}3)2] (R = Me, Et, {nBu}) is reported, displaying slow relaxation of the magnetization and magnetic hysteresis with non-zero coercive fields. Dynamic magnetic susceptibility experiments show that the three complexes possess anisotropy barriers of 34, 37 and 41 K (24, 29 and 26 cm???1); of similar magnitude to their \{{CoIII}2DyIII2\} counterparts. The replacement of the diamagnetic {CoIII} for paramagnetic {CrIII} ions results in significantly longer relaxation times, as observed via M(H) hysteresis at low temperatures, absent for the {CoIII} complexes. The present complexes are also compared to those of a similar {CrIII}???{DyIII} complex of formula [{CrIII}2DyIII2({OMe})2(O2CPh)4(mdea)2({NO}3)2] ({mdeaH}2 = N-methyldiethanolamine), which displays {SMM} behaviour with a larger anisotropy barrier of 77 K (54 cm???1) and even longer relaxation times. We show that the long relaxation times compared to the {CoIII} analogues are due to the significant magnetic exchange interactions between the {CrIII} and {DyIII} ions, resulting in the suppression of quantum tunnelling of the magnetization ({QTM}) and leading to a multilevel relaxation barrier. The height of the relaxation barrier in these {CrIII} systems is then shown to be directly related to the strength of the exchange interactions between the {CrIII} and {DyIII} ions, showing a clear route towards enhancing the slow magnetic relaxation of coupled {CrIII}???{DyIII} systems.

Bibliographical metadata

Original languageEnglish
Pages (from-to)3246-3256
Number of pages11
JournalChemical Science
Volume5
Issue number8
DOIs
Publication statusPublished - Jun 2014