Long-range and short-range magnetic correlations, and microscopic origin of net magnetization in the spin-1 trimer chain compoundCaNi3P4O14

Abstract

Spin-spin correlations and microscopic origin of net magnetization in the spin-1 trimer chain compound CaNi3P4O14 have been investigated by powder neutron diffraction. The present study reveals a three dimensional long-range magnetic ordering below 16 K where the magnetic structure consists of ferromagnetic trimers that are coupled ferromagnetically along the spin-chain direction (b axis). The moment components along the a and c axes arrange antiferromagnetically. Our study establishes that the uncompensated moment components along the b axis (m b ) result in a net magnetization per unit cell. The magnetic structure, determined in the present study, is in agreement with the results of recent first principles calculation; however, it is in contrast to a fascinating experimental prediction of ferrimagnetic ordering based on the periodicity of the exchange interactions in CaNi3P4O14. Our study also confirms the presence of broad diffuse magnetic scattering, due to 1D short-range spin-spin correlations, over a wide temperature range below ∼ 50 K down to a temperature well below the Tc. Total neutron scattering analysis by the reverse Monte Carlo (RMC) method reveals that the dominating spin-spin correlation above Tc is ferromagnetic and along the b axis. The nearest neighbor spin-spin correlations along the a and c axes are found to be weakly antiferromagnetic. The nature of the trimer spin structure of the short-range ordered state (above Tc) is similar to that of the 3D long-range ordered state (below Tc). The present investigation of microscopic nature of the magnetic ground state also explains the condition required for the 1/3 magnetization plateau to be observed in the trimer spin-chains. In spite of the S = 1 trimer chain system, the present compound CaNi3P4O14 is found to be a good realization of three dimensional magnet below the Tc = 16 K with full ordered moment values of ∼ 2 µB/Ni 2+ (1.98 and 1.96 µB/Ni 2+ for two Ni sites, respectively) at 1.5 K.PACS numbers: 75.30.-m, 75.25.-j, 75.40.Cx * akbera@barc.gov.in † smyusuf@barc.gov.in ‡ Present address:

Excitations in the spin-1 trimer chain compound CaNi3P4O14 : From gapped dispersive spin waves to gapless magnetic excitations

“…The presence of weak gapless magnetic excitations that persist up to ~ 100 K, is consistent with the previous neutron diffraction study [22] which revealed 1D short-range spin-spin correlations at T > T C .…”

“…The spin-chains in CaNi 3 P 4 O 14 are formed by edge-shared NiO 6 (Ni 2+ ; 3d 8 indicates the presence of short-range spin-spin correlations within the chains. Short-range spin-spin correlations were indeed found in neutron diffraction study as reported by us [22]. This may be noted that there are no phonon modes whose intensity increases with increasing temperature around the spin wave spectra.…”

“…However, no magnetization plateau was found for isostructural compounds based on Co-(S = 3/2) and Ni-(S = 1) having low spin values [17,22] which were predicted to be AFM trimer spin chain compounds [8]. However, later microscopic investigation of ground state properties by neutron powder diffraction suggested FM trimers in these compounds [17,22]. For the compounds ACo 3 P 4 O 14 and ANi 3 P 4 O 14 , magnetic long-range ordering temperatures were found to be higher (6.5 and 16 K, respectively [17,22]) in contrast to the T N =2.2 K for SrMn 3 P 4 O 14 [25].…”

Evidence for cluster spin glass phase with precursor short-range antiferromagnetic correlations in the B -site disordered Ca(Fe1/2Kumar1, Senyshyn2, Pandey3 2019Phys. Rev. B417210View full textAdd to dashboardCite

“…Neutron-scattering technique can provide evidence not only for the presence of LRO AFM structure but also for short-range ordered (SRO) AFM clusters of spins in the CSG systems. The presence of SRO AFM spin clusters gives rise to diffuse scattering in the neutron-scattering patterns [46,74,[94][95][96][97][98]. Accordingly, we carried out NPD measurements on powder samples of CFN to obtain direct evidence for the presence of AFM spin clusters.…”

Reverse Monte Carlo Algorithm and Maximum Entropy Principle for the Analysis of Positive Muon Spin Rotation and Relaxation Spectra

“…As examples of works, we cite the uncovering of correlations in the flux-line lattice of a type II superconductor [2], the characterization of the spin ice state in Ho 2 Ge 2 O 7 [3], the determination of the structure of liquids [4,5], and the investigations of structural and magnetic short-range-correlations for a large variety of magnetic compounds; see example of recent works in Refs. [6][7][8].…”