Magnetic states and the crystal volume of Nd2/3Ca1/3MnO3: analysis of phase transformations

Low Temperature Physics

et al. 2014

The exchange bias (EB) phenomenon has been found in Nd 2/3 Ca 1/3 MnO 3 perovskite. The phenomenon manifests itself as a negative horizontal shift of magnetization hysteresis loops.The EB phenomenon is evident of an interface exchange coupling between coexisting antiferromagnetic (AFM) and ferromagnetic (FM) phases and confirms the phase separated state of the compound at low temperatures. The EB effect is found to be strongly dependent on the cooling magnetic field and the temperature, which is associated with the evolution of spontaneous AFM -FM phase separated state of the compound. Analysis of magnetic hysteresis loops has shown that ferromagnetic moment M FM originating from the FM clusters saturates in a relatively low magnetic field about H ~ 0.4 T. The obtained saturation value M FM (1 T) ~ 0.45 μ B is in a good agreement with our previous neutron diffraction data.

Section: Resultssupporting

confidence: 90%

“…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 [22,23]. They lead to the coexistence of at least three different magnetic phases at low temperatures: two AFM charge-ordered ones and the FM charge-disordered one.…”

mentioning

confidence: 99%

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

Low Temperature Physics

et al. 2014

“…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.…”

Section: Introductionmentioning

confidence: 92%

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

Journal of Magnetism and Magnetic Materials

et al. 2012

A detailed study of the low-temperature magnetic state and the relaxation in the phase-separated colossal magnetoresistance Nd 2/3 Ca 1/3 MnO 3 perovskite has been carried out. Clear experimental evidence of the cluster-glass magnetic behavior of this compound has been revealed. Well defined maxima in the in-phase linear ac susceptibility χ′(T) were observed, indicative of the magnetic glass transition at T g ~ 60 K. Strongly divergent zero-field-cooled and field-cooled static magnetizations and frequency dependent ac susceptibility are evident of the glassy-like magnetic state of the compound at low temperatures. The frequency dependence of the cusp temperature T max of the χ′(T) susceptibility was found to follow the critical slowing down mechanism. The Cole-Cole analysis of the dynamic susceptibility at low temperature has shown extremely broad distribution of relaxation times, indicating that spins are frozen at "macroscopic" time scale. Slow relaxation in the zerofield-cooled magnetization has been experimentally revealed. The obtained results do not agree with a canonical spin-glass state and indicate a cluster glass magnetic state of the compound below T g , associated with its antiferromagnetic-ferromagnetic nano-phase segregated state. It was found that the relaxation mechanisms below the cluster glass freezing temperature T g and above it are strongly different. Magnetic field up to about m 0 H ~ 0.4 T suppresses the glassy magnetic state of the compound.

“…This compound is AFM/FM phase segregated at low temperatures, while existing as a paramagnetic single phase at room temperature ( Fig. 1) [29,30,31]. Below room temperature Nd 2/3 Ca 1/3 MnO 3 exhibits a sequence of phase transformations.…”

mentioning

confidence: 99%

Exchange bias in phase-segregated Nd2/3Ca1/3MnO3 as a function of temperature and cooling magnetic fields

Journal of Applied Physics

et al. 2014

Exchange bias (EB) phenomena have been observed in Nd 2/3 Ca 1/3 MnO 3 colossal magnetoresistance perovskite below the Curie temperature T C ~ 70 K and attributed to an antiferromagnetic (AFM) -ferromagnetic (FM) spontaneous phase segregated state of this compound. Field cooled magnetic hysteresis loops exhibit shifts toward negative direction of the magnetic field axis. The values of exchange field H EB and coercivity H C are found to be strongly dependent of temperature and strength of the cooling magnetic field H cool . These effects are attributed to evolution of the FM phase content and a size of FM clusters. A contribution to the total magnetization of the system due to the FM phase has been evaluated. The exchange bias effect decreases with increasing temperature up to T C and vanishes above this temperature with disappearance of FM phase.Relaxation of a non-equilibrium magnetic state of the compound manifests itself through a training effect also observed while studying EB in Nd 2/3 Ca 1/3 MnO 3 .