Effect of Y-doping on the magnetic and charge orderings in Nd2/3Ca1/3MnO3

Dolya

Journal of Magnetism and Magnetic Materials

et al. 2012

Self Cite

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.

Section: Introductionmentioning

confidence: 92%

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

Dolya

Journal of Magnetism and Magnetic Materials

et al. 2012

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“…This results in coexistence of self-organized charge-ordered (CO) and charge-disordered (CD) phases in a wide temperature range, as evidenced by an extended temperature hysteresis of the magnetic susceptibility in the CO region. Below T CO the compound exhibits two antiferromagnetic transformations at T N1 ~ 130 K and T N2 ~ 80 K, and a ferromagnetic one at T C ~ 70 K [29,30]. Therefore, at low temperatures below about 70 K at least three different magnetic phases, including two AFM charge-ordered phases and a FM charge-disordered one, coexist.…”

mentioning

confidence: 97%

“…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

Dolya

Journal of Applied Physics

et al. 2014

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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 .

“…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 [2,3]. They lead to the coexistence of at least three different magnetic phases at low temperatures: two antiferromagnetic charge-ordered ones (AFM) (their fraction is about 82%) and the ferromagnetic (FM) chargedisordered one (its phase fraction is about 18%) [4].…”

Section: Introductionmentioning

confidence: 99%

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

Feher

Low Temperature Physics

et al. 2012

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In the presented study we have revealed a giant exchange bias in a colossal magnetoresistance Nd 2/3 Ca 1/3 MnO 3 perovskite at low temperatures, evident of an intrinsic exchange coupling in this compound. The phenomena found confirms our previous assumption that the low-temperature magnetic structure of the compound is represented by small (nanosized) ferromagnetic clusters immersed within the charge-ordered antiferromagnetic matrix. Magnetic behavior of the Nd 2/3 Ca 1/3 MnO 3 perovskite is consistent with a cluster-glass magnetic state and does not agree with a classical spin-glass state observed in a variety of disordered magnetic systems. We think that the cluster-glass magnetic behavior of Nd 2/3 Ca 1/3 MnO 3 originates from the selforganized phase-separated state of the compound. The Cole-Cole analysis of the dynamic susceptibility at lowtemperatures has shown extremely broad distribution of relaxation times, indicating that spins are frozen at a "macroscopic" time scale. Slow relaxation of the zero-field-cooled magnetization has been experimentally revealed as well. This slow relaxation confirms the cluster-glass magnetic state of the compound. Two strongly different relaxation mechanisms were found: the first one is characteristic for temperatures below the freezing temperature T g ∼ 60 K, the second one is characteristic for higher temperatures. PACS