Ferrimagnetic Phase Transition Research Articles

Parametric Rietveld refinement and magnetic characterization of superparamagnetic iron oxide nanoparticles

This article describes the synthesis of two superparamagnetic iron oxide nanoparticles (SPIONs) covered with different ligands – hydrophobic (oleic acid (OA)) and hydrophilic (tetraethyl ammonium (TEA)) – and the investigation of the effects of thermal treatments on the crystal structure of TEA-SPIONs or OA-SPIONs using X-ray powder diffraction data and parametric Rietveld refinements; we stablished non-crystallographic models to describe how the oxidation processes take place with increasing temperatures for the different systems. The morphological and magnetic properties revealed the nanoparticles have a mean diameter of ∼10 nm in the solid state and are superparamagnetic at room temperature. Magnetization measurements confirmed the superparamagnetic state for both systems and revealed smaller particle sizes and narrower size distribution for OA-SPIONs than for TEA-SPIONs. The thermomagnetic analyses show only the ferrimagnetic phase transition of magnetite for OA-SPIONs while in the TEA-SPIONs, besides the ferrimagnetic phase transition there is the appearance of an antiferromagnetic one disclosing the evolution of hematite phase probably on the surface of magnetite due to thermal cycles.

Magnetic properties of (Nd,Ca)(Ba,La)Co2O5+δ tuned by the site-selected charge doping, oxygen disorder, and hydrostatic pressure

Comprehensive study of magnetic properties of the layer-ordered perovskites $\mathrm{N}{\mathrm{d}}_{1--x}\mathrm{C}{\mathrm{a}}_{x}\mathrm{B}{\mathrm{a}}_{1--y}\mathrm{L}{\mathrm{a}}_{y}\mathrm{C}{\mathrm{o}}_{2}{\mathrm{O}}_{5+\ensuremath{\delta}}$ is presented as a function of the site-selected charge doping $\mathrm{[}c=(x--y)/2+\ensuremath{\delta}\ensuremath{-}0.5,x\ensuremath{\le}0.2$ and $y\ensuremath{\le}0.1,0.07l\ensuremath{\delta}l0.84]$, oxygen disorder, and hydrostatic pressure $Pl10\phantom{\rule{0.16em}{0ex}}\mathrm{kbar}$. The single-phase oxygen-ordered orthorhombic phase exhibiting complex ferrimagnetic, antiferromagnetic, and metal-insulator phase transitions was found for a narrow oxygen range around $\ensuremath{\delta}\ensuremath{\sim}0.5\ifmmode\pm\else\textpm\fi{}0.1$. Significant difference between impact of hole $(cg0)$ and electron $(cl0)$ doping was observed depending on the site of cation substitution. Gradual enhancement of the Curie temperature ${T}_{\mathrm{C}}$ was observed over the whole range of $c$ to be unaffected by the local oxygen vacancy disorder. Maximum of the N\'eel temperature ${T}_{\mathrm{N}}$ at $c=0$ was found rapidly disappearing at $c=0.05$ for Ca/Nd substitution while it was maintained for La/Ba substitution, indicating that the oxygen vacancy disorder, especially for $\ensuremath{\delta}g0.5$, has a larger effect on antiferromagnetic phase than the charge doping. The temperature of metal-insulator transition ${T}_{\mathrm{MIT}}$ was found practically unchanged by either charge doping or disorder. The application of hydrostatic pressure slightly suppressed ${T}_{\mathrm{C}}$ and increased ${T}_{\mathrm{N}}$ by stabilization of the antiferromagnetic phase with the largest observed value of $\mathrm{d}{T}_{\mathrm{N}}/\mathrm{d}P=5.75\phantom{\rule{0.16em}{0ex}}\mathrm{K}/\mathrm{kbar}$. Complex magnetic behavior affected by hydrostatic pressure was accounted for by ferro- and antiferromagnetic interactions resulting from the charge separation and spin transitions.

Magnetic properties and magnetodielectric effect in Y-type hexaferrite Ba0.5Sr1.5Zn2-xMgxFe11AlO22

The effect of Mg substitution on structural, magnetic, and dielectric properties of Y-type hexaferrite Ba0.5Sr1.5Zn2-xMgxFe11AlO22 (x = 0, 0.4, 0.8, 1.2, 1.6, 2.0) prepared by the solid state reaction method was investigated. The X-ray diffraction patterns are analyzed by Rietveld refinement method and the hexagonal structure with R3−m was confirmed. The magnetic transition temperatures associated with the longitudinal conical to proper screw phase transition (T1) and proper screw to ferrimagnetic phase transition (T2) can be modulated by varying Mg content. For x ≤ 1.2 samples, the transition temperature T2 monotonically increases with increasing Mg substitution, suggesting the possibility that the helical spin order of Mg substituted Y-type hexaferrites is sustained up to higher temperatures than that of undoped samples. The saturation magnetization at room temperature increases to a maximum with Mg content x = 1.2 and then decreases with x. The variations of magnetic properties can be attributed to the difference in the preferential site for Zn and Mg and different distribution of Fe3+ ions over tetrahedral and octahedral sites. The results of magnetic field dependence of dielectric constant, i.e., magnetodielectric effect, at various temperatures imply that the doped samples show magnetically induced ferroelectricity up to 250 K. The intrinsic magnetodielectric effect is observed in all the samples. It is worthy to note that the magnetodielectric effect measured below 200 K increases with increasing Mg content, which is probably attributed to the variation of magnetic structures. The Mg-doped hexaferrites Ba0.5Sr1.5Zn2-xMgxFe11AlO22 may be potential candidates for application in magnetoelectric devices.

Ordering phenomena in a heterostructure of frustrated and unfrustrated triangular-lattice Ising layers.

We study critical and magnetic properties of a bilayer Ising system consisting of two triangular planes A and B, with the antiferromagnetic (AF) coupling J_{A} and the ferromagnetic (FM) one J_{B} for the respective layers, which are coupled by the interlayer interaction J_{AB} by using Monte Carlo simulations. When J_{A} and J_{B} are of the same order, the unfrustrated FM plane orders first at a high temperature T_{c1}∼J_{B}. The spontaneous FM order then exerts influence on the other frustrated AF plane as an effective magnetic field, which subsequently induces a ferrimagnetic order in this plane at low temperatures below T_{c2}. When short-range order is developed in the AF plane while the influence of the FM plane is still small, there appears a preemptive Berezinskii-Kosterlitz-Thouless-type pseudocritical crossover regime just above the ferrimagnetic phase transition point, where the short-distance behavior up to a rather large length scale exponentially diverging in ∝J_{A}/T is controlled by a line of Gaussian fixed points at T=0. In the crossover region, a continuous variation in the effective critical exponent 4/9≲η^{eff}≲1/2 is observed. The phase diagram by changing the ratio J_{A}/J_{B} is also investigated.

Variety of elastic anomalies in an orbital-active nearly itinerant cobalt vanadate spinel

We perform ultrasound velocity measurements on a single crystal of nearly-metallic spinel Co$_{1.21}$V$_{1.79}$O$_4$ which exhibits a ferrimagnetic phase transition at $T_C \sim$ 165 K. The experiments reveal a variety of elastic anomalies in not only the paramagnetic phase above $T_C$ but also the ferrimagnetic phase below $T_C$, which should be driven by the nearly-itinerant character of the orbitally-degenerate V 3$d$ electrons. In the paramagnetic phase above $T_C$, the elastic moduli exhibit elastic-mode-dependent unusual temperature variations, suggesting the existence of a dynamic spin-cluster state. Furthermore, above $T_C$, the sensitive magnetic-field response of the elastic moduli suggests that, with the negative magnetoresistance, the magnetic-field-enhanced nearly-itinerant character of the V 3$d$ electrons emerges from the spin-cluster state. This should be triggered by the inter-V-site interactions acting on the orbitally-degenerate 3$d$ electrons. In the ferrimagnetic phase below $T_C$, the elastic moduli exhibit distinct anomalies at $T_1\sim$ 95 K and $T_2\sim$ 50 K, with a sign change of the magnetoresistance at $T_1$ (positive below $T_1$) and an enhancement of the positive magnetoresistance below $T_2$, respectively. These observations below $T_C$ suggest the successive occurrence of an orbital glassy order at $T_1$ and a structural phase transition at $T_2$, where the rather localized character of the V 3$d$ electrons evolves below $T_1$ and is further enhanced below $T_2$.

Effect of Al Substitution on Structural, Magnetic, and Magnetocaloric Properties of Er6Fe23−xAlx (x = 0 and 3) Intermetallic Compounds

The structural, magnetic, and magnetocaloric properties of Er6Fe23−xAlx (x = 0 and 3) intermetallic compounds have been studied systematically. Samples were prepared using the arc furnace by annealing at 1073 K for one week. Rietveld analysis of XRD shows the formation of pure crystalline phase with cubic Fm-3m structure. Refinement results show that the unit cell volume decreases with increasing Al content. The Curie temperature Tc of the prepared samples was found to be strongly dependent on the aluminum content. This reduces magnetization and the ferrimagnetic phase transition temperature (Tc) from 481 K (for x = 0) to 380 K (for x = 3), is due to the substitution of magnetic element (Fe) by non-magnetic atoms (Al). With the increase of the Al content, a decrease in the values of magnetic entropy is observed. The magnitude of the isothermal magnetic entropy (|∆SM|) at the Tc decreases from 1.8 J/kg·K for x = 0 to 0.58 J/kg·K for x = 3 for a field change 14 kOe. Respectively, the relative cooling power (RCP) decreases with increasing Al content reaching 42 Jkg−1 for x = 0 to 28 Jkg−1 for x = 3.

Cation distribution dependent magnetic properties in CoCr2-xFexO4 (x = 0.1 to 0.5): EXAFS, Mössbauer and magnetic measurements.

In this report, we have examined the evolution of the structure and rich magnetic transitions such as a paramagnetic to ferrimagnetic phase transition at the Curie temperature (TC), spiral ordering temperature (TS) and lock-in temperature (TL) observed in the CoCr2O4 spinel multiferroic after substituting Fe. The crystal structure, microstructure and cation distribution among the tetrahedral (A) and octahedral (B) sites in the spinel lattice are characterised by X-ray diffraction, transmission electron microscopy, Extended X-ray Absorption Fine Structure (EXAFS) and Mössbauer spectroscopy. Due to the same radial distances of the first coordination shell in both tetrahedral and octahedral environments observed in EXAFS spectra, the position of the second coordination shell specifies the preference of more Fe ions towards the A site at x = 0.1. At x = 0.5, more Fe ions favour the B site. The cation distribution quantitatively obtained from the Mössbauer spectral analysis shows that while 60% of Fe ions occupy the A site in x = 0.1, 40% occupy it in x = 0.5. Surprisingly at x = 0.3, Fe ions are distributed equally among the A and B sites. dc magnetization reveals an increase in TC from 102 K to 200 K and in TS from 26 to 40 K with an increase in Fe concentration, indicating an enhancement in A-B exchange interaction at the expense of B-B. No report has until now demonstrated such an enhancement in TS either in pure or in doped CoCr2O4. Furthermore, frequency-dependent ac susceptibility (χ) data fitted with different phenomenological models such as the Néel-Arrhenius, Vogel-Fulcher and power law confirm a spin-glass and/or cluster-glass behaviour in nanoparticles of CoCr2-xFexO4.

Mg doping effect on the magnetic properties of Y-type hexaferrite Ba0.5Sr1.5Zn2−xMgxFe12O22

The microstructure and magnetic properties of Mg-doped Ba0.5Sr1.5Zn2Fe12O22 hexaferrites synthesized by the solid state method are investigated. All the undoped and doped samples show a sharp screw proper spin phase to collinear ferrimagnetic spin phase transition above room temperature, and transition temperature increases distinctly with Mg doping. It is noteworthy that all the samples exhibit another magnetic phase transition at a lower temperature T1, which is associated with the longitudinal conical to the proper screw phase transition. The transition temperature T1 can be modulated by varying Mg content, indicating that the longitudinal conical spin phase is stabilized by the Mg-substitution. The saturation magnetization at room temperature increases to a maximum with Mg content x = 0.8 and then decreases with x. The variations of magnetic properties can be ascribed to the difference in the preferential site for Zn and Mg and different distribution of Fe3+ ions over tetrahedral and octahedral sites. It is worth noting that the range for the intermediate-III phase increases significantly as x increases to 2.0, suggesting that Mg-doped samples may be display field-induced ferroelectric order at temperature close to RT and in wide magnetic-field regions. The room-temperature M-H curves at lower applied field indicate that magnetic-field-induced ferroelectric phase can be stabilized at zero magnetic field by the substitution by Mg2+ for Zn2+. The Mg-doped hexaferrites Ba0.5Sr1.5Zn2Fe12O22 may be potential candidates for applying in magnetoelectric devices.

Suppression of phase transitions at low temperature by chromium substitution in vanadium spinel Fe(V1−xCrx)2O4

Synchrotron powder diffraction, magnetization, and specific heat measurements have been used to investigate the structural and magnetic phase transitions in the spinel-type vanadate Fe(V1−xCrx)2O4 (0.0 ⩽ x ⩽ 1.0). We observed five different transitions in our polycrystalline samples. The canted-type ferrimagnetic phase transition accompanied by the lattice distortion was suppressed by Cr substitution (x = 0.2). Additionally, high-resolution synchrotron powder diffraction revealed that the low-temperature orthorhombic phase appears in FeV2O4 below 30 K and disappears by subtle Cr doping. In contrast, for x ⩾ 0.7, we observed a different magnetic transition of possibly conical-type ferrimagnetic ordering that did not induce significant lattice distortion at the transition temperature. We performed structural refinements for low-temperature phases and suggest that the crystal system of Fe(V1−xCrx)2O4 at 15K is an orthorhombic lattice for all x values. In the orthorhombic phase, a unique behaviour was observed, with the lattice constants a and b approaching each other as Cr doping increased. This behaviour can be explained by the change of orbitally ordered states of the Fe2+ ions.

Features of crystal and magnetic structures of solid solutions BaFe12-xDxO19 (D=Al3+, In3+; x=0.1) in a wide temperature range

The study of barium ferrites partially substituted by diamagnetic Al and In ions has been performed by the neutron diffraction method with high resolution. Both samples BaFe11.9D0.1O19 (\( D=Al\) and In) preserve a magnetoplumbit structure in a broad temperature range from 4.2K to 730K. The Invar effect was found in the low-temperature region in both samples. This unusual behavior of the unit cell was explained by changes of the regime of mutual rotations and tilts of the oxygen octahedra. The magnetic structure described by the Gorter model is saved up to the ferrimagnetic and paramagnetic phase transition temperature, 705K and 695K, for the Al- and In-substituted ions, respectively. The substitution of iron by aluminum or indium ions decreases the total magnetic moment of the investigated composition from \( 20 \mu_{B}\) (BaFe12O19) to 19 and \( 16.7 \mu_{B}\), respectively. A higher coercitivity was found \( H_{c}\sim 0.1\) T, for the In-substituted compositions, differently from \( H_{c}\sim 0.007\) T of the Al-doped ones because of the frustration of the magnetic structure. The decrease of ambient temperature increases microstresses in crystallites because of the increasing influence of the magnetic subsystem.

Effect of Gd/Nd doping on the magnetic properties of PrMnO3

A study on temperature dependent magnetic properties of single-phase orthorhombic perovskites system associated with space group Pbnm compounds Pr1−x(Gd/Nd)xMnO3 (x = 0.3, 0.5, 0.7) was carried out. A magnetization reversal is observed below the Néel temperature (TN), in dc magnetization measurements (at 50 Oe) in the doped compounds. This may be due to the antiparallel coupling between the two magnetic sublattices (|Pr + Gd/Nd|and Mn). With lowering of temperature, the |Pr + Gd/Nd| ions begin to polarize under the negative internal field due to canted moment of Mn moments. The hysteresis plot taken at 50 K shows a ferrimagnetic characteristic and the presence of spin canting of ions in the magnetic sublattices. Arrott plot indicates field induced second-order paramagnetic to ferrimagnetic (PM–FiM) phase transition in this system.

Development of a Photoresponsive Organic–Inorganic Hybrid Magnet: Layered Cobalt Hydroxides Intercalated with Spiropyran Anions

Abstract To develop an organic–inorganic hybrid photomagnet, we performed the intercalation of sulfonate-substituted spiropyran anions into layered cobalt hydroxides, obtaining the photoresponsive compound, Co(OH)1.84(nSPSO3)0.16·0.8H2O (CoLHSP; nSPSO3: 1′,3′,3′-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-indoline]-5′-sulfonate). After UV irradiation (313 nm), the optical and magnetic properties of CoLHSP clearly changed. A new band emerged in the absorption spectrum at 564 nm, corresponding to the π–π* transition in the open form of nSPSO3. Moreover, the photoisomerization of nSPSO3 induced a new ferrimagnetic phase transition at 10 K in the temperature dependence of DC and AC magnetic susceptibilities in addition to the ferrimagnetic phase transition at 15 K for the unirradiated sample. Analyzing the magnetic measurements before and after UV irradiation, we estimated the phototransformation ratio of the magnetic phase in CoLHSP at approximately 40%.

About the Role of Fe-Ions in the Formation of Magnetocaloric Effect in Ho(Co1-xFex)2Compounds

A study of crystalline structure, magnetic and magnetocaloric properties of Ho(Co1−xFex)2 (x = 0.09, 0.12) intermetallic compounds has been undertaken. Phase composition was controlled by X-ray di raction analysis. Magnetic properties were measured within the temperature range 4.2 350 K in magnetic elds up to 7 T. Magnetic ordering temperatures corresponding to paramagnetic ferrimagnetic phase transitions were found to be 199 K and 258 K respectively. Temperature dependences of heat capacity for these compounds have been inferred for the temperature interval 77 340 K. Comparison of magnetocaloric e ect (MCE) values determined by direct measurement and by calculation was carried out as well. It was found that signi cant MCE peak broadening occurs for higher iron concentration in the compound.

Large reversible room-temperature magnetocaloric effect in the Ba0.5Sr1.5Zn2Fe12O22-related hexaferrites

The magnetic and magnetocaloric effect (MCE) of Mg or Cu-doped Ba0.5Sr1.5Zn2Fe12O22 hexaferrites synthesized by the sol-gel method are investigated. The Ba0.5Sr1.5Zn2Fe12O22 shows a sharp paramagnetic to ferrimagnetic phase transition and a large conventional MCE at around room temperature. By the partial substitution of Zn with Mg or Cu, the magnetic transition temperature as well as the maximum MCE temperature can be tuned in the range of 300 and 375K while keeping the maximum MCE nearly unchanged, which are beneficial characteristics for their application as near room-temperature magnetic refrigerants. For Ba0.5Sr1.5Zn2Fe12O22, it is found that the maximum values of magnetic entropy change –ΔSM and relative cooling power (RCP) are 1.27J/kg K and 124J/kg for ΔH=4.4T, respectively. Given its advantages, such as large RCP, suitable working temperature, low-cost raw materials, easy to synthesize, and environment-friendly, the Ba0.5Sr1.5Zn2Fe12O22 related hexaferrites may be potential candidates for room-temperature magnetic refrigeration.

Calorimetry of Low-Dimensional Metal-Assembled Complexes

A kind of molecule-based magnets, metal-assembled complexes tend to possess low-dimensionalities for their magnetic lattices. Heat capacity calorimetry is a powerful tool for elucidation of the magnetic properties of metal-assembled complexes. Heat capacity measurements were carried out for the one-dimensional metal-assembled complexes MnIICuII(obbz).nH2O (obbz = oxamidobis(benzoato), n = 1, 5) and two-dimensional metal-assembled complexes NBu4[MIICrIII(ox)3] (Bu = n-butyl; M = Cu, Fe; ox = oxalato) and PPh4[MnIICrIII(ox)3] (Ph = phenyl). MnIICuII(obbz).5H2O undergoes an antiferromagnetic phase transition at TN = 2.18 K and have a heat capacity hump above TN, which can be reproduced well by the spin quantum number S = 2 one-dimensional ferromagnetic Heisenberg model with the intrachain exchange interaction J/kB = 0.75 K, where kB is the Boltzmann constant. Partially dehydrated MnIICuII(obbz)H2O exhibits a ferrimagnetic phase transition at Tc = 17 K and shows a heat capacity tail above Tc, which can be reproduced rather by the S = 2 two-dimensional ferromagnetic Heisenberg models. NBu4[CuIICrIII(ox)3], NBu4[FeIICrIII(ox)3], and PPh4[MnCr(ox)3] indicate ferromagnetic phase transitions at TC = 6.98 K, 12.0 K, and 5.85 K, respectively, and heat capacity tails above TC, which can be reproduced well by the two-dimensional ferromagnetic Heisenberg models of honeycomb lattice with the intralayer exchange interactions J/kB = 5.0 K, 2.5 K, and 0.95 K, respectively. Keywords: Heat capacity, high-temperature series expansion, magnetic entropy, magnetic phase transition, metal-assembled complex, molecule-based magnet, low dimensionality, spin wave.

Specific heat and magnetocaloric effect studies in multiferroic YMnO3

Multiferroic bulk YMnO3 sample was prepared through the solid state reaction method. After characterizing the sample structurally, a systematic investigation of magnetization and specific heat has been undertaken over a temperature range 2–300 K under different magnetic fields. Based on these studies, it has been found that the sample exhibited a paramagnetic to ferrimagnetic phase transition of spin glass type at ~42 K that could be attributed to spin cantering. The magnetic transition peak seen in the magnetic entropy change versus temperature curves became broader with increasing magnetic field. A large magnetic entropy change of ~1 J mol−1 K−1 was obtained under a magnetic field change of 0–10 T.

Magnetic and low temperature phonon studies of CoCr2O4 powders doped with Fe(III) and Ni(II) ions

Extensive temperature-dependent phonon studies and low-temperature magnetic measurements of CoCr2−xFexO4 (for x=0.5, 1 and 2) and Co0.9Ni0.1Cr2O4 polycrystalline powders are presented. The main aim of these studies was to obtain information on phonon and structural properties of these compounds as well as strength of spin–phonon coupling in the magnetically ordered phases. IR and Raman spectra show that doping of CoCr2O4 with Fe(III) ions leads to broadening of bands and appearance of new bands due to the formation of inverted spinel structure. In contrast to this behavior, doping with 10mol% of Ni(II) ions leads to weak increase of band width only. Magnetization measured as a function of temperature and external magnetic field showed that magnetic properties of Co0.9Ni0.1Cr2O4 sample are similar to those reported for pure CoCr2O4, i.e., partial substitution of Ni(II) for Co(II) leads to slight shift of the ferrimagnetic phase transition at TC and spiral spin order transition at TS towards lower values. The change of crystallization preference induced by incorporation of increasing concentration of Fe(III) ions in the spinel lattice causes significant increase of TC and decrease of TS. The latter transition disappears completely for higher concentrations of Fe(III). The performed temperature-dependent IR studies revealed interesting anomalous behavior of phonons below TC for CoCr1.5Fe0.5O4 and Co0.9Ni0.1Cr2O4, which was attributed to spin–phonon coupling.

Field-induced phase transitions of the ferrimagnetic state in Er0.9Lu0.1Fe2O4

The isothermal magnetization of the Er0.9Lu0.1Fe2O4 compound was investigated and analyzed carefully in this work. A magnetocaloric effect measurement was employed to reveal complex ferrimagnetic phase transitions. A field-induced phase transition was found in the temperature range of 208 to 240 K for applied fields from 0.7 to 1.5 T. A complex magnetic phase diagram was established based on the magnetization curves. Ferrimagnetic clusters with Fe-ion interactions of different origins were hypothesized to be responsible for the ferrimagnetic phase separation.

Temperature-dependent XRD, IR, magnetic, SEM and TEM studies of Jahn–Teller distorted NiCr2O4 powders

Abstract In the present work we report detailed structural, magnetic and phonon properties of NiCr 2 O 4 powders synthesized via a simple coprecipitation method. Temperature-dependent XRD as well as temperature-dependent IR studies reveal that cubic to tetragonal phase transition is lowered due to size effects. Observed changes in the IR spectra indicate that the paramagnetic–ferrimagnetic phase transition taking place at 74 K is related to further lowering of symmetry to orthorhombic system. Assignment of modes was proposed and factor group analyses in three possible symmetries were carried out. Our results show strong anomalies due to the Jahn–Teller tetragonal distortion and weak due to the orthorhombic distortion and onset of collinear ferrimagnetic order. Shifts of wavenumbers observed below 31 K, where the onset of antiferromagnetic ordering occurs, were attributed to spin–phonon interactions.

Low Temperature Magnetic Behavior of Ca3Co4O x Polycrystalline Material

Misfit layered Ca3Co4O9 samples have been fabricated by solid-state reaction method. X-ray diffraction analysis showed that the samples have the c-axis oriented monoclinic structure. The temperature dependence of the DC magnetization of the sample fabricated was investigated in an applied field of 2000 Oe. Magnetization of the sample increased smoothly down to 20 K, then increased rapidly with decreasing temperature, suggesting a transition to the ferrimagnetic phase. M–H analysis indicated a paramagnetic behavior between 20 and 300 K and hysteretic effect below 20 K which corresponds to paramagnetic–ferrimagnetic phase transition. The ferrimagnetisms are most likely caused by interlayer coupling between the Ca2CoO3 and CoO2 subsystems in unit cell.