Magnetic Order in Two-Dimensional Arrays of Nanometer-Sized Superparamagnets

Scheinfein, M. R.; Schmidt, Kevin; Heim, K. R.; Hembree, G. G.

doi:10.1103/physrevlett.76.1541

Cited by 104 publications

(93 citation statements)

References 24 publications

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“…12 At room temperature, such systems can display an antiferromagnetic, a superparamagnetic, and an in-plane ferromagnetic phase. 13 Superparamagnetism has also been observed in Co/Cu͑100͒ films, 14 and the magnetic structure above the Curie temperature was ascribed to 2D Heisenberg spin blocks. 15 One interest in Langmuir-Blodgett ͑LB͒ films with magnetic ions is their possible use for testing different theoretical models of order in 2D magnets.…”

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confidence: 87%

Evidence for magnetic ordering in ultrathin gadolinium Langmuir-Blodgett films

et al. 1997

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confidence: 87%

Evidence for magnetic ordering in ultrathin gadolinium Langmuir-Blodgett films

et al. 1997

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“…The exchange interaction between the grains leads to the formation of long-range magnetic order appearing below a certain temperature [3,[23][24][25], which is called the ordering temperature T ord . For Ising model [24 and 35] the ordering temperature in granular magnets with FM coupling is related to the intergrain exchange interaction as T ord = z n H ex , where z n = 6 is the coordination number for three dimensional cubic lattice.…”

Section: A Granular Magnetsmentioning

confidence: 99%

“…Numerous papers were devoted to magnetic anisotropy and magneto-dipole interaction [15][16][17][18][19][20][21][22]. Much less is known about the exchange interaction between magnetic grains [23][24][25][26][27]. The influence of the intergrain exchange coupling on the magnetic state of the whole granular magnet are currently understood, however the microscopic picture of the intergrain exchange interaction is still missing.…”

Section: Introductionmentioning

confidence: 99%

Competition of the Coulomb and hopping-based exchange interactions in granular magnets

Udalov

Beloborodov

2017

Phys. Rev. B

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We study exchange coupling due to the interelectron Coulomb interaction between two ferromagnetic grains embedded into insulating matrix. This contribution to the exchange interaction complements the contribution due to virtual electron hopping between the grains. We show that the Coulomb and the hopping based exchange interactions are comparable. However, for most system parameters these contributions have opposite signs and compete with each other. In contrast to the hopping based exchange interaction the Coulomb based exchange is inversely proportional to the dielectric constant of the insulating matrix ε. The total intergrain exchange interaction has a complicated dependence on the dielectric permittivity of the insulating matrix. Increasing ε one can observe the ferromagnet-antiferromagnet (FM-AFM) and AFM-FM transitions. For certain parameters no transition is possible, however even in this case the exchange interaction has large variations, changing its value by three times with increasing the matrix dielectric constant.

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“…The transition to in-plane ferromagnetic behavior of the magnetic structure at an average island radius aϾ30 Å ͑at about 13 ML of Fe͒ has been observed. 27 For the Fe clusters with a radius of 44 Å the local order parameter has a nonzero value up to 580 K. 27 Thus a change of magnetic behavior in our Ni film in the thickness range 15-26 Å may also be due to cluster formation. The domain pattern of our thick films had a small sensitivity to the field, whether applied parallel or perpendicular to the film plane ͑in our experiments up to 4000 and 70 A/m, respectively͒.…”

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confidence: 99%