Charge ordering, internal structural parameters, and magnetic susceptibility of Nd2∕3Ca1∕3MnO3: driving forces of a phase transition

Abstract

The temperature dependences of the long diagonals dMn–O of the MnO6 octahedron and the magnetic susceptibility χ of Nd2∕3Ca1∕3MnO3 in the temperature interval 100–290K are investigated. The functions dMn–O(T) and χ(T) are found to have anomalies in the charge-ordering range (Tco≈212K). The sharp decrease of the diagonal dMn–O2s agrees with phase-transition notions, according to which the spatial modulation of the charge density is due to the modulation of the Mn–Mn bond lengths. The most likely driving forces of the transition are the Peierls lattice instability and Jahn–Teller stability of the MnO6 octahedron at the Mn3+ ions. The hysteresis of the temperature dependence χ(T) in the paramagnetic region shows indirectly that structural phase separation occurs together with the transition. The parameters of the function χ(T) indicate that ferromagnetic clusters consisting of one, two, or three ion pairs Mn3+–Mn4+ form in the system in the temperature intervals 274K⩽T⩽290K, 224K⩽T⩽252K, and 130K⩽T⩽198K, respectively.

Cluster glass magnetism in the phase-separated Nd2/3Ca1/3MnO3 perovskite

“…Earlier we have found that its low temperature magnetic nanoscale phase-segregated state [1,2] originates from the charge ordering that takes place at much higher temperature T CO ≈ 212 K [3]. Charge ordering phase transformation in Nd 2/3 Ca 1/3 MnO 3 is a first order phase transition of martensitic (nondiffusion) type which leads to the self-organized coexistence of charge ordered and charge disordered phases in the wide temperature range below the room temperature.…”

“…Charge ordering phase transformation in Nd 2/3 Ca 1/3 MnO 3 is a first order phase transition of martensitic (nondiffusion) type which leads to the self-organized coexistence of charge ordered and charge disordered phases in the wide temperature range below the room temperature. Extended temperature hysteresis of the magnetic susceptibility in the charge ordering region is one of the evidences of the nonequilibrium phase-segregated state [3]. Below T CO the compound exhibits a sequence of magnetic transformations: two antiferromagnetic ones at T N1 ~ 130 K and T N2 ~ 80 K, and a ferromagnetic one at T C ~ 70 K. They lead to the coexistence of at least three different magnetic phases at low temperatures: the two antiferromagnetic charge ordered ones (AFM) (their fraction is about 82%) and the ferromagnetic charge disordered (FM) one (its phase fraction is about 18%) [4].…”

Direct evidence of the low-temperature cluster-glass magnetic state of Nd2/3Ca1/3MnO3 perovskite

“…The charge ordering phase transformation in Nd 2/3 Ca 1/3 MnO 3 , which takes place at T co ≈ 212 K [1], is of the first-order martensitic type. It leads to the self-organized coexistence of charge-ordered (CO) and charge-disordered (CD) phases in a wide temperature range below the room temperature.…”

“…It leads to the self-organized coexistence of charge-ordered (CO) and charge-disordered (CD) phases in a wide temperature range below the room temperature. Extended temperature hysteresis of the magnetic susceptibility in the charge ordering region is one of the evidences of the nonequilibrium phase-segregated state [1].…”

Exchange bias associated with phase separation in the Nd2/3Ca1/3MnO3 manganite

“…The charge ordering phase transformation in Nd 2/3 Ca 1/3 MnO 3 , which takes place at T CO ≈ 212 K [21], is of the first order martensitic type. It leads to the self-organized coexistence of charge-ordered (CO) and charge-disordered (CD) phases in a wide temperature range below the room temperature.…”