μSR Spectrum Reconstruction Using Monte Carlo Approach: A Preliminary Study

Abstract

A possible method to reconstruct μSR spectra using Monte Carlo approach presented. Three issues carefully addressed for the simulations, that is automatic muon sites estimations, movement of muon due to gradient electrostatic potential and thermal fluctuation. All minima within the unit cell need to be included for more realistic theoretical μSR spectra. The optimum scale of gradient potential and thermal fluctuation needed to achieve a realistic result. Additional μSR spectra can be revealed in comparison with the simulation at lower thermal fluctuation.

The Effect of Interaction Weight on Dipole Field Calculations to Reconstruct the La₂CuO₄ μSR Spectrum

“…The order from lowest to higher electrostatic potential energy are M2, M1, M5, M3, and M4. The M5 site has an agreement with previous prediction [23,24], while M3 and M4 has never been investigated before due to negligibly small peak from μSR spectrum. Higher resolutions in μSR experiments are proposed to reveal the possibility of a new peak above 419 G until about 7200 G as shown in maximum field value at 7041 G from site M5b in Table .…”

“…La2CuO4 (LCO) is one of the best candidates for μSR spectrum reconstruction due to well investigated by muon [1][2][3][4][5][6][7][8] and neutron [9][10][11][12][13][14][15]. Several possible muon sites in LCO also has been investigated intensively using dipole field calculation, electrostatic potential and supercell structure relaxation [16][17][18][19][20][21][22][23][24], yet their possible muon sites still cannot be used directly to reconstruct the μSR spectrum theoretically. Additional mechanisms are necessarily to make the theoretical spectrum fit the internal field from μSR experiment result.…”

“…Additional mechanisms are necessarily to make the theoretical spectrum fit the internal field from μSR experiment result. Our previous study [24] shows a robust and automatic way to reconstruct μSR spectrum using Monte Carlo approach but still lack of an additional mechanism to achieve more realistic spectrum.…”

“…Sulaiman et al [17], Suter et al [20] and Rozlan et al [25] tried to explain the reduction by calculating the hyperfine contact field from LCO, but all of them has similar result that the hyperfine contact field can only reduce about 10% of dipole field result while 50% reduction is required. The commonly used solution for the reduction problem is by decreasing the copper magnetic moment from neutron diffraction until the dipole field fit the μSR experiment data [24,26]. Reducing magnetic moment shows a promising way to reconstruct the μSR spectrum but lead to contradiction magnetic moment value between neutron diffraction and theoretical result.…”

“…In this work, we modify the dipole field equation by adding interaction weight to reduce the dipole field result. The modified dipole field result will be compared with the commonly used dipole field with a reduction constant [24,26]. The effect of modified dipole field to theoretical μSR spectrum from all potential minima will be investigated.…”