The dependence of magnetic properties on temperature for rare earth ErCrO3 chromites

Multiferroic ErCrO₃ was synthesized and the detailed magnetic as well as ferroelectric properties were investigated. The dc magnetization shows that ErCrO₃ undergoes a antiferromagnetic ordering at T_N = 133 K due to the Cr³⁺–Cr³⁺ followed by weak ferromagnetic ordering. Around T_SR ≈ 22 K, ErCrO₃ exhibits a spin reorientation from Γ₄ to Γ₁. And the stability of the ferromagnetic Γ₄ phase increases with the applied magnetic field increasing. Furthermore, at lower temperature, it shows weak antiferromagnetic ordering of Er³⁺. We also present the low temperature polarization data for ErCrO₃ and find a remarkable decreasing of polarization around T_N = 133 K on increasing temperature, this effect might be due to the coupling between magnetic and ferroelectric order parameters, and the magnetic field suppresses the polarization which demonstrates convincingly the strong magnetoelectric (ME) coupling in ErCrO₃.     

XAS and XPS analysis of double magnetic transition,canonical spin glass behavior and magnetoresistance in LaMn1-xCoxO3 (0.1 ≤ x ≤ 0.5) system

Polycrystalline LaMn_1-xCo_xO₃ (0.1≤ x ≤ 0.5) samples were synthesized using conventional ceramic method. Rietveld refined X-ray diffraction pattern revealed the single-phase orthorhombic crystal structure of all the samples with the space group Pbnm. Temperature-dependent magnetic measurements performed in field cooled (FC) and zero field cooled (ZFC) mode at 10² Oe exhibit the onset of double transition in x = 0.3–0.5 compositions. The ordering temperature rises with an increase in Co concentration. FC and ZFC studies show the presence of glassy state below the ordering temperature in all samples; confirmed using a. c. susceptibility measurements. The a. c. susceptibility data are analyzed using power law and the existence of canonical spin glass is revealed. Magnetic hysteresis studies demonstrate the enhanced ferromagnetism amid the presence of unsaturated magnetization with an increase in Co doping. The presence of double transition and spin glass state is attributed to the competing ferromagnetic and anti-ferromagnetic interactions between the Co and Mn ions present in the system. The system also depicts the presence of appreciable value of magnetoresistance ~42% at 8 T magnetic field in x = 0.5 sample. These properties are interpreted through valence and spin states of Mn and Co ions, being confirmed from electronic structure studies using X-ray absorption spectroscopy (XAS) at L_3,2- edges of respective ions along with O K-edge for all samples (0.1≤ x ≤ 0.5). After meticulous analysis and conjoining the results obtained from magnetization and XAS studies, it is found that cobalt is present in high spin Co²⁺ and high/low spin Co³⁺-state. Charge transfer multiplet calculation done at L_3,2 edges of Mn and Co ions confirm the presence of Mn³⁺/Mn⁴⁺ and Co²⁺/Co³⁺ states consistent with XAS results. X-ray photoelectron spectroscopy performed at Mn2p, Co2p, and O1s -edges further substantiate the reasons behind the properties exhibited by the present system.     

Influence of rare-earth La3+ ion doping on microstructural,magnetic and dielectric properties of Mg0.5Ni0.5Fe2-xLaxO4 (0 ≤ x ≤ 0.1) ferrite nanoparticles

A series of La³⁺ ion doped magnesium nickel ferrites, Mg_0.5Ni_0.5Fe_2-xLa_xO₄ (0 ≤ x ≤ 0.1) having a cubic spinel structure were prepared by the co-precipitation method. Various characterization techniques, including X-ray diffractometer (XRD), high resolution transmission electron microscopy (HR-TEM), electron spin resonance (ESR) and vibrating sample magnetometer (VSM) were used to investigate structural and magnetic properties. The average crystallite size decreases and lattice parameter increases with La³⁺ ion doping and lie in the range of 12–7 nm and 8.347–8.361 Å respectively. Analysis of ESR spectra reveals that, g-value with La³⁺ ion addition decreases from 2.57 to 2.12. The saturation magnetization and the coercivity decrease with increasing rare-earth content. Magnetic-hysteresis (M − H) loop shifts from a ferromagnetic to a superparamagnetic nature with La³⁺ ion addition. The dielectric study was carried out in the frequency range of 1 KHz to 4000 KHz and temperature ranging 30 °C–350 °C using the impedance analyzer. The dielectric constant decreases with increasing frequency and the La³⁺ ion concentration. The dielectric loss of the sample increases with increasing temperature. The magnetic properties of the synthesized nanoparticles make them a potential material for stable ferrofluid application and the low tangent loss value makes these material a potential candidate for frequency-based applications.     

Impact of rare earth europium (RE-Eu3+) ions substitution on microstructural,optical and magnetic properties of CoFe2−xEuxO4 nanosystems

In this study, pure cobalt ferrite (CoFe₂O₄) nanoparticles and europium doped CoFe₂O₄ (CoFe_2−xEu_xO₄; x = 0.1, 0.2, 0.3) nanoparticles were synthesized by the precipitation and hydrothermal approach. The impact of replacing trivalent iron (Fe³⁺) ions by trivalent rare earth europium (RE-Eu³⁺) ions on the microstructure, optical and magnetic properties of the produced CoFe₂O₄ nanoparticles was studied. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra exposed the consistency of a single cubic phase with the evidence of Eu₂O₃ phases for x ≥ 0.2. FTIR transmittance spectra showed that, the all investigated samples have three characteristic metal-oxygen bond vibrations corresponding to octahedral B-site (υ₁ and υ₂) and tetrahedral A-site (υ₃) around 415 cm⁻¹, 470 cm⁻¹ and 600 cm⁻¹ respectively. XRD and energy dispersive X-ray spectroscopy studies affirmed the integration of RE-Eu³⁺ ions within CoFe₂O₄ host lattice and decrease of average crystals size from 13.7 nm to 4.7 nm. Transmission electron microscopy (TEM) analysis showed the crucial role played by RE-Eu³⁺ added to CoFe₂O₄ in reducing the particle size below 5 nm in agreement with XRD analysis. High resolution-TEM (HR-TEM) analysis showed that the as-synthesized spinel ferrite, i.e., CoFe_2−xEu_xO₄, nanoparticles are single-crystalline with no visible defects. In addition, the HR-TEM results showed that pure and doped CoFe₂O₄ have well-resolved lattice fringes and their interplanar spacings matches that obtained by XRD analysis. Magnetic properties investigated by the vibrating sample magnetometer technique illustrated transformation of magnetic state from ferromagnetic to superparamagnetic at 300 K resulting in introducing RE-Eu³⁺ in CoFe₂O₄ lattice. At low temperature (~5 K) the magnetic order was ferromagnetic for both pure and doped CoFe₂O₄ samples. Substitution of Fe³⁺ ions in CoFe₂O₄ nanoparticles with RE-Eu³⁺ ions optimizes the sample nanocrystals size, cation distribution and magnetic properties for many applications.     

Crystal structure,electrical and magnetic properties of anion-deficient perovskite-like Ba3SmFe2O7.5

Anion-deficient perovskite-like Ba₃SmFe₂O_7.5 was prepared using a glycerol–nitrate synthesis. Using high-temperature X-ray diffraction in situ a crystal structure transition temperature range 800 and 840 °C was established. These results were further confirmed by high-temperature dilatometric analysis. The average thermal expansion coefficient (TEC) of Ba₃SmFe₂O_7.5 is about 12.8 × 10⁻⁶ K⁻¹ between 25 °C and 800 °C. Magnetic experiments proved an excellent phase purity of the oxide and reveal that Fe³⁺ ions stay in high and intermediate spin states in a ratio of 75% and 25% respectively.     

Effect of indium substitution on the structure and magnetic characteristics of ternary iron-based nitrides

In this paper, the structure and magnetic behaviour of antiperovskite In_xFe_4-xN have been investigated systematically. The crystal lattice becomes larger and the Curie temperature decreases with increasing x. The magnetic state changes from a ferromagnetic to a glassy state. In addition, an obvious spin glass (SG) behaviour has been revealed in In_0.6Fe_3.4N (x = 0.6) with a freezing temperature of T₀ = 73 K, dynamical exponent of zν = 5.51, and flipping time of τ₀ = 4.26 × 10⁻¹¹ s. The origin of the SG behaviour in In_0.6Fe_3.4N may be attributed to atomic disorders at Wyckoff position 1a or ferromagnetic frustrations, or the both.     

Field tuning magnetic phase transition in Dy0.5Tb0.5FeO3 single crystal

RFeO₃ is an ideal candidate for the fabrication of spintronic devices, and its rare earth site doping is an important means to regulate and produce many unique spin behaviors. In this work, we report a high-quality Dy_0.5Tb_0.5FeO₃ single crystal grown by optical floating zone method and its magnetic properties are studied explicitly. A type-Ⅱ spin switching effect and suppressed spin reorientation transition are found in the Magnetization vs Temperature curves in Dy_0.5Tb_0.5FeO₃. In the temperature region of spin reorientation transition, the transition of Fe³⁺ magnetic sublattice configuration becomes very complicated by the influence of competitive interaction with magnetic Dy³⁺/Tb³⁺ ions. Interestingly, a field tunable double-hysteresis loop is observed near the antiferromagnetic transition temperature of rare earth ions sublattice, which has never been reported in RFeO₃ family compounds. By studying the dependence of double-hysteresis loop at different temperatures, the magnetic phase transition and spin reorientation transition induced by the applied magnetic field are inferred. This novel physical phenomenon helps us understand the mechanism of spin configuration transition better at low temperatures.     

Structural and magnetic properties of iron in graphite

Pure and impure graphite powders, and two samples of highly oriented pyrolytic graphite (HOPG) have been studied by X-ray diffraction, electron microscopy, magnetometry and ⁵⁷Fe Mössbauer spectrometry in order to identify the distribution of iron impurities and establish their role in the weak ferromagnetism of some of these materials. Pure graphite powder (99.9995%) shows straightforward diamagnetic behavior, with quantum oscillations at 4 K. The impure (>99%) powder gives a ferromagnetic signal exhibiting little temperature dependence in the temperature range 1.8–300 K, due to the presence of roughly isometric inclusions of metallic iron and cementite (Fe₃C) about 100 nm in size. These inclusions are not superparamagnetic. The HOPG-ZYA and -ZYB samples show similar, but highly anisotropic ferromagnetic signals with a saturation magnetization of 1–5 × 10⁻³ A m² kg⁻¹, due to inclusions of thin Fe₃C platelets in the graphite sheet with a diameter of ≈1 μm and diameter to thickness ratio >10. These platelets form Frisbee-shaped rings around primary lens-shaped inclusions of cubic (Ti, V)C. It is important to account quantitatively for the presence of these metallic, iron-rich inclusions before claiming that the origin of any weak ferromagnetic behavior of graphite is related to intrinsic lattice defects.     

Synthesis, structural and magnetic properties of nanostructured Ca0.9Gd0.1MnO3 obtained by modified glycine nitrate procedure (MGNP)

Ca_0.9Gd_0.1MnO₃ nanopowders with perovskite type crystal structure were synthesized by modified glycine nitrate procedure. Nanopowders were prepared by combining glycine with metal nitrates and/or metal acetates in their appropriate stoichiometric ratios. Modification of the procedure was performed by partial replacement of nitrates by acetates, in order to control the burn-up reaction. Obtained Ca_0.9Gd_0.1MnO₃ powders were calcinated in the temperature interval from 850 °C to 950 °C for 10 min. Properties such as phase evolution, lattice parameters, chemical composition and magnetic properties were monitored by DTA, X-ray diffraction, SEM/EDS and magnetic measurements. Magnetic measurements performed at the sample with the smallest crystallite size showed that a 10% of Gd³⁺ substituted Ca²⁺ ions changes antiferromagnetic properties of CaMnO₃ by the introduction of ferromagnetic interaction due to a double exchange between Mn³⁺ and Mn⁴⁺ ions. Presence of competing interactions and their randomness lead to a formation of a spin glass state below Neel temperature T_N = 110 K. From the high temperature magnetic susceptibility measurements effective magnetic moment of manganese ions is determined which lies between the values for Mn³⁺ and Mn⁴⁺ ions.     

Influence of Ti ions valence states on the optical and magnetic properties of GdCr1-xTixO3 (0≤x≤0.05)

The vacancy defects, optical and magnetic properties of GdCr_1-xTi_xO₃ (0≤x ≤ 0.05) polycrystalline samples were investigated in this research. The crystal structural analyses show that the orthorhombic perovskite structure exists in all the samples. The positron annihilation spectra reveal that the vacancy defects and local electron density vary with the change of Ti ions valence states. The magnetic measurements show that the antiferromagnetic transition is shifted to lower temperature with the replacement of Ti ions in Cr sites, and the value of spin reorientation caused by the exchange interaction between Gd³⁺ ion and Cr³⁺ ion can be influenced by the change of Ti ions valence states, which rises from x = 0 to 0.04 and then decreases at x = 0.05 sample. Simultaneously, the optical band gap decreases from 2.7 eV to 0.8 eV with the introduction of Ti ions into the lattice, the result can provide a reference for improving optical activity of rare-earth chromium oxides.     

Spin valve effect in sputtered FL-MoS2 and ferromagnetic shape memory alloy based magnetic tunnel junction

In the last decade, two-dimensional (2D) transition metal dichalcogenides have been introduced with great significance in the spintronic devices for their extraordinary electrical, optical, and spin-dependent properties. In this work, we have fabricated a few-layer molybdenum disulfide (FL-MoS₂) (~6 nm) as a non-magnetic spacer layer in Ni–Mn–In/FL-MoS₂/Ni–Mn–In magnetic tunnel junction (MTJ) using DC magnetron sputtering. FL-MoS₂ thin film sandwiched between two ferromagnetic shape memory alloy based electrodes exhibit semiconducting behavior, confirmed by current-voltage (I–V) characteristics and temperature dependent resistance measurement. The fabricated MTJ shows spin valve effect in the presence of an external magnetic field. The tunneling magnetoresistance (TMR) has been recorded in 10 K–300 K temperature range. The highest TMR ratio of 0.51% was obtained at a low temperature ~10 K, corresponding to the spin polarization of ~5%. This TMR ratio reduces to a value of 0.032% as the temperature of the device increases up to 300 K, displaying a finite TMR at room temperature. A detailed study of thickness and temperature-dependent magnetization versus magnetic field (M ? H) hysteresis loops of Ni–Mn–In thin films has been performed to understand the complex TMR behavior. The present study paves the way for the use of sputtered FL-MoS₂ and ferromagnetic shape memory alloy in ultrafast spintronics for advanced magnetic devices application.     

Structure and magnetism in the Zn–Mn–O system: A candidate for room temperature ferromagnetic semiconductor

The reactivity of the Zn–Mn–O system, prepared by conventional ceramic routes using ZnO and MnO₂ as starting materials are described and correlated with the magnetic response. X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy techniques have been used for the structural analysis. The ferromagnetic response is unambiguously determined to be due to the simultaneous presence of Mn⁺³ and Mn⁺⁴ ions at the Zn diffusion front into the manganese oxide grain. Thus, it is demonstrated that Mn does not incorporate into the ZnO lattice substitutionally, but it is the Zn that diffuses into the manganese oxide grains, acting as a retardant of the manganese reduction, Mn⁺⁴ → Mn⁺³. At the diffusion front, both ions coexist and their spins couple ferromagnetically through a double exchange mechanism. This mechanism explains the origin of the room temperature ferromagnetism recently discovered in Zn–Mn–O system as a promising material for spintronic devices.     

Spin reorientation,normal and inverse magnetocaloric effects in heavy rare-earth iron garnets

Experiments for heavy rare-earth iron garnets Ho₃Fe₅O₁₂ and Er₃Fe₅O₁₂ show a compensation effect characterized by a near zero magnetization at 134 K and 80 K, respectively. The magnetic entropy change calculated according to the Maxwell's relation is shown to be positive and negative, indicating both normal and inverse magnetocaloric effects exist in the sample. The critical temperature (134 K for Ho₃Fe₅O₁₂, 80 K for Er₃Fe₅O₁₂) of the two types of magnetocaloric effect occurs at almost the same temperature as the compensation point. However, the compensation effect is attributed to the multiple exchange interactions among the octahedral sites Fe³⁺, the tetrahedral sites Fe³⁺ and the dodecahedral sites R³⁺, while the reversal of the magnetocaloric effect is originated from the spin reorientation. The maximum magnetic entropy change of the normal magnetocaloric effect is 4.72 J kg⁻¹ K⁻¹ for Ho₃Fe₅O₁₂ at 34 K and 4.94 J kg⁻¹ K⁻¹ for Er₃Fe₅O₁₂ at 24 K, respectively. Moreover, all the positive slopes of basic Arrott plots suggest only the second-order phase transition existing in Ho₃Fe₅O₁₂ and Er₃Fe₅O₁₂.     

Influence of Ce addition on the structural,magnetic, and magnetocaloric properties in La0.7−xCexSr0.3MnO3 (0≤x≤0.3) ceramic compound

We report improvement in the magnetocaloric properties of Ce-doped lanthanum manganites. Polycrystalline La_0.7−xCe_xSr_0.30MnO₃ (0≤x≥0.3) samples were prepared using the conventional solid-state reaction method with phase purity and structure confirmed using X-ray diffraction. Temperature dependent magnetization measurements and Arrott analysis reveal second order ferromagnetic transition in parent sample and as well as in doped sample with Curie temperature decreasing progressively with increasing Ce-concentration from ~370 K for x=0.0 to 310 K for x=0.30. Magnetic entropy change (ΔS_M) was calculated by applying the thermodynamic Maxwell equation to a series of isothermal field dependent magnetization curves. A large ΔS_M associated with the ferromagnetic–paramagnetic transition in La_0.7−xCe_xSr_0.30MnO₃ samples has been observed. The value of ΔS_M was found to increase with Ce-doping up to x=0.15 and the highest value of 2.12 J kg⁻¹ K⁻¹ (at ΔH=2 T) was observed for La_0.55Ce_0.15Sr_0.30MnO₃ sample near the Curie temperature of 356 K. Also, improved relative cooling power of ~122 J kg⁻¹ was observed for the same sample. Due to the large magnetic entropy change and high Curie temperature, the La_0.55Ce_0.15Sr_0.30MnO₃ sample is suggested to be used as potential magnetic refrigerants for magnetic refrigeration technology above room temperature.     

A four-spin ring with alternating magnetic interactions formed by pyridine-substituted nitronyl nitroxide radicals and Gd(III) ions: Crystal structure and magnetic properties

A novel complex, [Gd(hfac)₃(NIT-5-Br-3py)]₂ (hfac = hexafluoroacetylacetonat, NIT-5-Br-3py = 2-(4,4,5,5-tetramethyl-3-oxylimidazoline-1-oxide)-5-bromo-3-pyridine) has been synthesized and characterized structurally and magnetically, in which a NIT-5-Br-3py molecular acts as a bridge ligand linking two Gd(III) ions through the oxygen atom of the N–O group and nitrogen atom from the pyridine ring to form a four-spin system. The fitting result of the magnetic susceptibility shows two different magnetic interactions between Gd(III) ion and NIT-5-Br-3py in one complex: a weak ferromagnetic interaction (J₁ = +2.60 cm⁻¹) through the N–O group, and a much weaker antiferromagnetic (J₂ = −0.24 cm⁻¹) interaction through pyridine ring.     

Preparation of multiferroic composites of BaTiO3–Ni0.5Zn0.5Fe2O4 ceramics

Magneto-electric coupling in ceramic composites formed by ferroelectric and ferromagnetic phases can be obtained via an adequate mechanical coupling between the individual piezoelectric and magnetostrictive phases (product property). In the present work, the possibility of forming diphase ferroelectric–ferromagnetic ceramics has been investigated. Composites of xBaTiO₃–(1 − x)Ni_0.5Zn_0.5Fe₂O₄ with x = 0.5, 0.6 and 0.7 were prepared according two different procedures: (i) by direct mixing powders of perovskite BaTiO₃ and Ni_0.5Zn_0.5Fe₂O₄ spinel prepared by solid state and (ii) by coprecipitating Fe^III–Ni^II–Zn^II nitric salts in a NaOH solution in which the BaTiO₃ powders were previously dispersed. Optimum processing parameters for good homogeneity, densification and for a reduction of the chemical reactions at the interfaces ferroelectric-ferrite were found. A temperature and composition-dependent magnetic order is present in all the composites, with a dilution effect of the magnetisation due to the presence of the non-ferromagnetic phase. A diffuse ferroelectric–paraelectric transition due to the BaTiO₃ phase was identified by the temperature-dependence of the permittivity and losses, showing that at room temperature the material preserves a ferroelectric order. The interfaces play important roles in the dielectric properties, causing space charge effects and Maxwell–Wagner relaxation, particularly at low frequencies and high temperatures. The combined ferroelectric and magnetic ordering will result in magneto-electric coupling in this material; further investigations are necessary.     

Structure and magnetic properties of a novel branch-like one-dimensional cyano-bridged assembly [Cu(L)]3[Fe(CN)6]2·8H2O (L = 6,13-dimethyl-6-nitro-1,4,8,11-tetraazabicyclo[11.1.1]pentadecane)

The one-dimensional coordination polymer like fern branch, [Cu^II(L)]₃[Fe^III(CN)₆]₂·8H₂O (1), which is linked by azamacrocyclic copper(II) complex and iron(III) hexacyanide, has been synthesized and characterized by single crystal X-ray crystallography and magnetic susceptibility measurement (L = 6,13-dimethyl-6-nitro-1,4,8,11-tetraazabicyclo[11.1.1]pentadecane). Compound 1 shows a weak ferromagnetic coupling between the copper(II) and low spin iron(III) ions in the one-dimensional chain structure.     

Magnetic and phonon transitions in B-site Co doped BiFeO3 ceramics

Magnetic susceptibility and phonons have been characterized in multiferroic Bi(Fe_1−xCo_x)O_3−δ ceramics for x=0.0, 0.05, and 0.10 (BFO100xCo) as functions of temperature. A preferred (100) crystallographic orientation and increasing average oxygen vacancies were observed in BFO5Co and BFO10Co. The Fe and Co K-edge synchrotron X-ray absorptions revealed mixed valences of Fe³⁺, Fe⁴⁺, Co²⁺, and Co³⁺ ions in BFO5Co and BFO10Co, which exhibit a ferromagnetic (or ferrimagnetic) phase below room temperature due to appearance of ferromagnetic B–O–B (B=Fe and Co) superexchange interactions. Field–cooled (FC) and zero–field–cooled (ZFC) magnetic susceptibilities exhibit a significant spin-glass splitting below room temperature in BFO5Co and BFO10Co. Two Raman-active phonon anomalies at ~170 K (or 200 K) and ~260 K were attributed to the Fe³⁺–O–Co³⁺ and Co³⁺–O–Co³⁺ magnetic orderings, respectively. This work suggests that the low-spin Co²⁺–O–Co²⁺, Fe³⁺–O–Fe³⁺ (or Fe⁴⁺), and high-spin Co²⁺–O–Co²⁺ superexchange interactions are responsible for phonon anomalies at ~290 (or ~300 K), ~400, and ~470 K (or ~520 K) in BFO5Co and BFO10Co.     

Electrical transport properties driven by magnetic competition in hole-doped perovskite Pr1-xBaxMnO3 (0.25 ≤ x ≤ 0.36)

In this work, polycrystalline Pr_1-xBa_xMnO₃ (0.25 ≤ x ≤ 0.36) ceramics were synthesized, and their magnetic and electrical transport properties were systematically studied. All samples show two metal-insulator transitions (MITs) corresponding to the high temperature T_MI1 and low temperature T_MI2, respectively, besides the non-Griffith phase above the ferromagnetic (FM) transition temperature T_C. Combining the results of the transport and magnetic properties, it is found that the FM transition temperature T_C coincides with the temperature T_MI1, which is linearly related to the A-site ionic radius mismatch variance σ², indicating the enhancement of FM interactions due to the increase of the degree of B-site ordering of Mn³⁺/Mn⁴⁺ ions. The positive correlation between ferromagnetic insulators (FMI) and magnetic interactions, including the FM and short-range antiferromagnetic (AFM) interactions, is confirmed. It is suggested that the first MIT at T_MI1 is attributed to the Mn³⁺/Mn⁴⁺ double exchange interactions and the second MIT at T_MI2 is closely related to the suppression of the AFM interactions under the internal FM field induced by the Mn³⁺/Mn⁴⁺ DE interactions. This work provides not only a theoretical understanding on the origin of MIT at low temperature, but also a new way for adjusting the FMI in perovskite manganese oxide Pr_1-xBa_xMnO₃ for application.     

Synthesis and magnetic properties of ceramic MgO porous film

Ordered porous MgO films with pore diameters in the 15–28 nm range have been prepared on porous anodic alumina substrates at 573 K in a fixed O₂ pressure of 1.4 × 10⁻⁴ mbar using DC-reactive magnetron sputtering. X-ray diffraction and scanning probe microscope observations have revealed that homogeneous MgO ceramics with face-centered cubic structure are formed with a highly ordered nanopore array arranged in a close packed hexagonal pattern. The results of magnetic measurements have shown that the porous MgO ceramics possess remarkable room temperature ferromagnetism and the maximum saturation magnetization along the out-of-plane direction was as high as 78 emu/cm³. Experimental and theoretical results suggest that oxygen vacancies and the unique porous structure of the films are responsible for the high magnetization. These results provide new insights into magnetic ordering in undoped dilute ferromagnetic semiconductor oxides and may be useful in the development of MgO-based spintronics devices and novel multifunctional materials.