Intergranular Exchange Coupling Research Articles

Macroscopic phenomenon of exchange coupling and microscopic effect on magnetization reversal in sintered Nd–Fe–B magnets

Permanent magnets of Nd13.5Fe79.18M1.52B5.8 and Nd13.5Fe79.76M0.94B5.8 were prepared, respectively, via strip casting, jet milling and sintering followed by annealing. By adding the non-ferromagnetic elements M (Al, Cu, Ga and Zr) into the magnets, it could not only modify the microstructure, but also regulate the exchange coupling effect in the sintered magnets. From the macroscopic point of view, the recoil loops exhibit spring behavior in Nd13.5Fe79.76M0.94B5.8, indicating that the energy barrier can be overcome by the intergranular exchange coupling. From the microcosmic point of view, the exchange coupling can increase the domain wall size by suppressing the nucleation of reversed domains, and so the activation volume increases with thermal activation. In Nd13.5Fe79.76M0.94B5.8 the exchange coupling effect is stronger, and both the coercivity of 15.0 kOe and the remanence of 14.3 kGs are a little higher than those of Nd13.5Fe79.18M1.52B5.8 magnets in which the content of non-ferromagnetic elements is a little higher and the exchange coupling effect is weaker. Thus, the exchange coupling does not decrease the coercivity due to the exchange coupling suppressing the nucleation of reversed domains, though the microstructure is inhomogeneous in the sintered magnets of Nd13.5Fe79.76M0.94B5.8. Reducing the defect size and decreasing the defect concentration should be a practical way to improve the coercivity in Nd–Fe–B permanent magnets.

Epitaxial Growth of Large-Scale 2D CrTe2 Films on Amorphous Silicon Wafers With Low Thermal Budget.

2D van der Waals (vdW) magnets open landmark horizons in the development of innovative spintronic device architectures. However, their fabrication with large scale poses challenges due to high synthesis temperatures (>500 °C) and difficulties in integrating them with standard complementary metal-oxide semiconductor (CMOS) technology on amorphous substrates such as silicon oxide (SiO2) and silicon nitride (SiNx). Here, a seeded growth technique for crystallizing CrTe2 films on amorphous SiNx/Si and SiO2/Si substrates with a low thermal budget is presented. This fabrication process optimizes large-scale, granular atomic layers on amorphous substrates, yielding a substantial coercivity of 11.5 kilo-oersted, attributed to weak intergranular exchange coupling. Field-driven Néel-type stripe domain dynamics explain the amplified coercivity. Moreover, the granular CrTe2 devices on Si wafers display significantly enhanced magnetoresistance, more than doubling that of single-crystalline counterparts. Current-assisted magnetization switching, enabled by a substantial spin-orbit torque with a large spin Hall angle (85) and spin Hall conductivity (1.02 × 107 ℏ/2e Ω⁻¹ m⁻¹), is also demonstrated. These observations underscore the proficiency in manipulating crystallinity within integrated 2D magnetic films on Si wafers, paving the way for large-scale batch manufacturing of practical magnetoelectronic and spintronic devices, heralding a new era of technological innovation.

High-coercivity SmFe12-based anisotropic sintered magnets by Cu addition

We achieved a record-high coercivity of 1.40 T in a SmFe12-based ThMn12-type anisotropic sintered magnet. This magnet was prepared by sintering jet-milled powder made from strip-cast alloys with a nominal composition of Sm8Fe73.5Ti8V8Al2Cu0.5, using the conventional process for anisotropic sintered magnet production. Detailed microstructural investigations conducted using scanning electron microscopy and transmission electron microscopy revealed that the formation of Fe-lean intergranular phases (with < 20 at.% of Fe) surrounding the fine SmFe12 phase grains resulted in the high coercivity. Nanobeam electron diffraction patterns showed that these Fe-lean intergranular phases (IGPs) exhibiting excellent wettability in this magnet are mainly composed of two phases: a hexagonal close-packed Mg-type Sm-based phase and a primitive cubic CsCl-type SmCu-based phase, which co-exist in the same intergranular region. Such Fe-lean IGPs minimize the intergranular exchange coupling in the SmFe12 main phase, which contributes to the high coercivity, as revealed by magneto-optical Kerr effect microscopy. Overall, this study provides detailed microstructure-coercivity correlations and insights for the future development of high-performance SmFe12-based sintered magnets.

Microstructure optimization and magnetic properties enhancement of hot pressed Nd-Fe-B magnets via grain boundary diffusion of NdCu powder

Microstructure modification of Nd-Fe-B magnets plays a key role in regulating magnetic properties. In this work, low melting point NdCu alloy was added to improve the coercivity of NdFeB ribbons, and then high coercivity nanocrystalline NdFeB magnets were prepared by hot pressing sintering (HPS). The result shows that the coercivity of NdFeB powders blending with 15 wt% Nd-Cu powders obtained a maximum increment, as high as 12.69 kOe. After HPS, the fully dense magnets with excellent magnetic properties are obtained. Microstructure analysis confirmed that the Nd-Cu alloy has diffused into the interior of hard magnetic grains along the grain boundary during heat treatment. The enrichment of Nd, Pr, and Cu in the grain boundary phase weakens the magnetism of the grain boundary phase and reduces the intergranular exchange coupling. This is the main reason for the coercivity enhancement. In addition, the diffusion of Nd70Cu30 can significantly improve the thermal stability of the magnets.

Improving intergranular phase and enhanced coercivity: A grain boundary diffusion of non-heavy rare earth PrNdAl alloy in sintered Nd-Fe-B magnets

The optimization of microstructure is an important strategy to improve the coercivity. In this paper, non-heavy rare earth PrNdAl alloy was selected as the diffused source to enhance the coercivity and improve the microstructure. The results show that the diffusion of PrNdAl alloy can greatly enhance the coercivity, achieving an increment of 31.1% compared to that of as-prepared sample. The diffusion of PrNdAl alloy does not change the crystal structure of intergranular phase in the triple-junction region. Three factors contribute to the improvement of coercivity. One is the enhancement of magnetic hardening of main phase grain surface, owing to the formed (Nd, Pr)2Fe14B shell. The other is the weakening of intergranular exchange coupling among grains, which is aroused by the reduced Fe content in RE-rich phase. The last is that the formed continuous RE-rich phase between grains contribute to the enhancement of magnetic isolation effect. In addition, the metallurgical behavior of elements and the evolution of intergranular phase are investigated.

Evaluation of core-shell structure and grain boundary structure in multi-main-phase Nd-Y-Fe-B sintered magnet by grain boundary modification

The grain boundary modification by Pr64Fe12Al9Ga15 addition was performed in the B-lean Nd-Y-Fe-B multi-main-phase (MMP) magnets. The effects of the additive on the microstructure and magnetic properties were investigated. A pronounced coercivity enhancement was achieved from 4.96 kOe to 8.15 kOe with 2 wt% Pr64Fe12Al9Ga15 addition, while the coercivity tended to be invariable with further increasing of Pr64Fe12Al9Ga15 content to 4, 6, and 8 wt%. Detailed microstructure analysis revealed that the significant amounts of RE6Fe13(Ga, Al)1 intergranular phase were generated by introducing Pr64Fe12Al9Ga15 additive in the B-lean Nd-Y-Fe-B MMP magnets. The formation of RE6Fe13(Ga, Al)1 contributed to the optimization of the distribution of grain boundary (GB) phase, strengthening the intergrain magnetic isolation. However, the further increases of the additive content led to the agglomeration of RE6Fe13(Ga, Al)1 in the triple junction region, which caused a reduction in remanence. Meanwhile, excessive addition for additives revealed that the thicker GB layer was unessential to further increase in coercivity, the intergranular exchange coupling had already been decoupled in magnets with adequate addition. In addition, more Pr atoms were primarily substituting the Nd atoms, but Y atoms were not substituted by Pr in the shell region of matrix grains. It was deemed that the magnetic anisotropy of the grain shell was essentially unchanged even with the formation of Pr-rich shell. These results reported here enlighten the microstructure design of Nd-Y-Fe-B MMP magnets.

Influence of exchange coupling interaction on coercivity in 2:17-type SmCo-based high temperature permanent magnets

The intergranular exchange coupling interaction in Sm(CobalFe0.10Cu0.10Zr0.03)7.2 high temperature permanent magnets with different isothermal aging time was studied. The magnet isothermally aging for 24 h with higher coercivity at room temperature exhibits a weaker exchange coupling, while that aging for 4 h with a relatively small temperature coefficient of coercivity shows a stronger exchange coupling. Microstructure and microchemistry analysis indicated that Cu gradually enriches in the cell boundaries with the prolongation of isothermal aging time, decreasing the exchange coupling strength. Theoretical analysis results revealed that with the increase of temperature, the cells gradually get exchange decoupled and demagnetized independently, and the exchange coupling strength between cells decreases, which slows down the decline of coercivity. It is proposed that an optimized temperature coefficient of coercivity requires a stronger exchange coupling at room temperature, conducing to a more significant compensation effect with the increase of temperature.

Impact of sonication time on the structural and magnetic features of CoFe2O4/Ni0.8Cu0.1Zn0.1Fe2O4 hard-soft nanocomposites

Hard/soft (H/S) CoFe2O4/Ni0.8Cu0.1Zn0.1Fe2O4 nanocomposites (NCs) were prepared via ultrasonic irradiation method under different ultrasonication durations (10, 20, 30, 40, 50, and 60 min). The structure and morphology of these nanocomposites were analyzed through XRD, FT-IR, SEM, TEM, and EDX techniques, which confirmed the successful preparation of the desired nanocomposites. The crystallites/particles size was found to reduce with increasing ultrasonication duration. The magnetic properties of H/S CoFe2O4/Ni0.8Cu0.1Zn0.1Fe2O4 NCs prepared via ultrasonication method under different ultrasonication durations (10, 20, 30, 40, 50, and 60 min) were investigated through measurements of magnetization against the magnetic field (M-H) at 10 and 300 K. The soft character of the prepared NCs at room temperature depicted their superparamagnetic behaviors. At extremely low temperatures (T = 10 K), all H/S ferrite NCs revealed opened M-H hysteresis loops, indicating their ferrimagnetic behavior at low temperatures. All H/S NCs do not reveal any kind of anomalies in their M-H curves. Additionally, the SFD (switching field distribution) analysis pointed out a single peak in dM/dH against H curves. It was found that the intergranular exchange coupling interactions are more dominant than the intergranular dipolar interactions. Such a result indicates that the current synthesis method is useful to produce good exchange-coupled hard/soft ferrite NCs. It was also observed that the Ms and Mr values at both 10 and 300 K are decreasing with rising the ultrasonication duration. However, the Hc value was found to increase with rising ultrasonication duration, reaching a maximum value under an ultrasonication duration of 30 min, then, the Hc value decreases with further rising the ultrasonication duration. The plausible reasons for the variations in magnetic parameters were discussed.

Structural evolution and improvement of magnetic properties of hot-deformed CeFeB magnets with Nd70Cu30 addition

The low magnetic properties of Ce-based magnets limit their application. In this paper, we aim to improve the coercivity, remanence and maximum energy product of hot-deformed CeFeB magnets by adding low melting Nd70Cu30 alloy. It is found that the addition of Nd70Cu30 remarkably improve the thermal stability and magnetic properties of Ce–Fe–B-based hot-deformed magnets. It is shown by analyzing the microstructure that the proportion of the coarse grain region decreases and the proportion of the liquid region increases in the magnet after adding Nd70Cu30 alloy. The former reduces the nucleation sites of magnetization reversal and the latter weakens the intergranular exchange coupling. Furthermore, the typical core-shell structure was found to be formed in magnets. TEM observation demonstrated that Nd, Ce and Cu were enriched at grain boundaries. Two Curie temperatures were obtained due to different types of 2:14:1 phase, i.e. the incipient CeFeB phase and the newly formed (Nd, Ce)2Fe14B hard magnetic phase. Because of the combined effect of (Nd, Ce)2Fe14B phase and intercrystalline phase, the comprehensive magnetic properties of hot-deformed Ce–Fe–B-based magnets with Nd70Cu30 addition are greatly improved.

Structure and magnetic properties of Ga doped Nd13.65Fe74.15B5.6Co6.6 ribbons

The addition of low melting point Ga changed the crystallization process and microstructure of the Nd13.65Fe74.15B5.6Co6.6 ribbons. The Ga addition improves the glass-forming ability of the ribbons, and the ribbons melt-spun at 25 m/s are composed of Nd2(Fe, M)14B phases with different Nd contents and Nd-rich amorphous grain-boundary phase. Nd2(Fe, M)14B grains have a gradient size of 50–300 nm, also, the large-sized grains are slightly rich in Fe-Co, and the small-sized ones are rich in Nd. Compared to the Ga-free alloy, 0.6 at% Ga addition narrows the grain boundary width to 5.5 ± 4.5 nm, promotes the enrichment of Ga atoms at grain boundaries and form Nd(Fe, Co)1.62Ga0.04 composition, improved the intergranular exchange coupling and magnetic properties of the ribbons most significantly, increasing the coercivity and remanence by 52.6% and 36.6% respectively. Besides, the microstructure models changed by Ga addition are established, and the corresponding solidification processes and magnetic mechanisms are discussed.

Temperature Dependence and Microstructure Effects on Magnetic Properties of FePt(B, Ag, C) Film.

A FePt(B, Ag, C) granular film was formed from post-annealed B4C(1.0 nm)/FePt(Ag, C) layers at a substrate temperature of 470 °C for 2 min. The 6 nm thick FePt(B, Ag, C) film demonstrates high perpendicular magnetic anisotropy (Ku = 2.83 × 107 erg/cm3 at 100 K) and out-of-plane coercivity (Hc = 38.0 kOe at 100 K). The Ku and out-of-plane Hc are respectively increased from 38% and 46% between 350 K and 50 K. The sample with a thickness of 8 nm also shows a similar trend for magnetic properties; however, the tiny magnetization kink which may come from rare Fe-B or disordered FePt grains was observed in the easy axis loop. The intrinsic (ΔHint = 12.6 kOe) and extrinsic switching field distribution (ΔHext = 1.62 kOe) were characterized by major and minor loops to correlate the microstructural grains. The coupled FePt grains grown on a single MgTiON grain were observed in a high-resolution transmission electron microstructure (HRTEM) image. This small intergranular exchange coupling was defined by estimating the magnetic cluster size (46.6 nm) from ΔHext and the average grains size (28.2 nm) from TEM images. The temperature dependence of coercivity was fitted to further understand the magnetization reversal process. The lower microstructural parameter was evidenced in the imperfect grain morphology.

Analysis of Adjacent Track Erasure in the HAMR Media

Writing closely spaced tracks in the cross-track direction helps increase the storage density but leads to erasure of the adjacent tracks. This phenomenon is called adjacent track erasure (ATE). This article aims to establish the presence and numerical extent of ATE in different heat-assisted magnetic recording (HAMR) media. We find that thermal exchange coupled composite (ECC) media can be more susceptible to ATE compared with single layer FePt media of equivalent thickness. We implement optimization techniques to reduce the ATE in different media and increase the recording signal to noise ratio (SNR) in this process. While the ATE in single layer FePt media seems to be relatively impervious to changes in the applied field angle, small field angles appear to reduce the ATE for the high $T_{c}$ thermal ECC media. However, small angle also reduces the SNR, leading to the conclusion that 30° actually yields the best SNR even in the presence of overwrite. Introducing a finite intergranular exchange coupling improves the writing performance of the single layer FePt and reduces the ATE. We rigorously calculate the thermal decay constant and use it to evaluate the performance of pulsed laser recording. Finally, we establish a hypothesis that helps explain the presence of ATE in different HAMR media. We believe the ATE is proportional to the thermal stability factor at a temperature just below the write temperature. The proposed hypothesis correctly predicts the ATE in the single layer FePt media assuming coherent rotation. Our results can help increase the HAMR storage density and make HAMR media resistant to the ATE.

Switching Field Control by Utilizing Ferromagnetic Grain Boundary in Cap Layer for CoPt-Based Full Granular Media

Investigation of magnetic properties and nanostructure for full granular media with CoPt−Gd2O3 granular cap layers (CLs) of various Gd2O3 content were conducted. Media with low surface roughness of 0.19 nm is maintained even though Gd2O3 content is reduced from 30 to 5 vol%, which is lower than that of media with CoPtCrB continuous CL. The result is supported by surface morphology observed by transmission electron microscopy. According to cross section element analysis, homogeneous nanostructure in the thickness direction with one- text on-one columnar growth of magnetic grain is observed. Reduction of Gd2O3 content increases indirect intergranular exchange coupling through CL which results in media with higher nucleation field and lower saturation field than that of media with CoPtCrB continuous CL. Furthermore, at a CL thickness of 6 nm, when Gd2O3 content is reduced from 30 to 15 vol%, switching field distribution is reduced from 0.11 to 0.05. These results suggest that the reduction of Gd2O3 content of the CoPt−Gd2O3 granular CL is effective to reduce the switching field distribution of the full granular media to be lower than that of media with CoPtCrB continuous CL while retaining the extremely smooth media surface.

Extremely flat surface full granular media with cap layer consisting of high-Ku CoPt grains and ferromagnetic oxide grain boundaries

Investigation of magnetic properties and nanostructure of stacked media with a CoPt-B2O3 granular recording layer (GRL) and granular cap layers (CL) with CoPt and a typical ferromagnetic oxide of rare earth (RE) oxide (RE oxide: Gd2O3, Nd2O3, Sm2O3, and CeO2) are reported. CoPt-RE oxide granular layer shows higher saturation magnetization and magnetic anisotropy than that of CoPtCrB continuous layer. In stacked media with CoPt-Gd2O3 granular CL (9 nm), nucleation field increases from 0.7 to 0.8 kOe and saturation field decreases from 21.5 to 12.5 kOe with comparable values to those of CoPtCrB continuous CL. This indicates that CoPt-RE oxide granular CL is effective to control intergranular exchange coupling. Reduction of coercivity distribution ratio (∆Hc/Hc) from 0.15 to 0.09 which is comparable to that of CoPtCrB continuous CL when CoPt-Gd2O3 granular CL thickness is changed from 4 to 9 nm is observed. This means CoPt-Gd2O3 granular CL is effective to reduce switching field distribution. Furthermore, significant reduction of surface roughness (Ra) for media with CoPt-Gd2O3 granular CL (9 nm) from 0.32 to 0.25 nm is observed. This reveals that CoPt-RE oxide granular CL has a great impact to induce stacked media with flat surface. Based on the cross-section observation by TEM, the media with CoPt-Gd2O3 granular CL shows continuous structure of grain boundaries from the GRL up to the CL and which results in one-on-one growth of magnetic grain with homogeneous columnar structure. Focusing on the surface morphology, media with CoPt-Gd2O3 granular CL shows smoother surface than that of media with CoPtCrB continuous CL which supports the Ra evaluation result. These results indicate that the employment of granular CoPt-RE oxide for CL is not only to reduce switching field distribution but also to flatten surface of the stacked media.

Model Building and Anisotropy of PrFeB Permanent Magnetic Materials

This paper considers that the crystal grains of HDDR Pr2Fe14B permanent magnetic material are cubic, the size is 0.3 μm, and the crystal grains are in simple cubic accumulation. It is considered that there are boundary phases between grains. It is assumed that the boundary phases are non-magnetic phases with the thickness of d, and evenly distributed between grains. The anisotropy expression of single grain boundary is given considering structure defect and intergranular exchange coupling interaction. Based on micro-magnetic simulation calculation, the variation of the average anisotropy of a single grain with the structural defects and boundary phases was calculated. The results show that when the thickness of structural defects is constant, the average anisotropy of a single grain decreases with increasing of grain boundary phase thickness, and while the thickness of grain boundary phase is constant, it also decreases with increasing of structural defect thickness.

Coercivity enhancement of hot-deformed (Ce,Nd,Pr)-Fe-B magnets by grain boundary diffusion of Pr-Cu alloy

The coercivity of hot-deformed (Ce,Nd,Pr)-Fe-B magnet was enhanced from 1.44 T to 1.71 T by the addition of 3 wt% Pr-Cu powders for grain boundary diffusion. Microstructure analysis has shown that the formation of thick grain boundary phase with non-ferromagnetism can well isolate the adjacent main phase grains and weaken the intergranular exchange coupling, which is beneficial to coercivity enhancement. Moreover, the size of platelet shaped grains inhibited by liquid phase inside the ribbon is also one of the reasons for the increase of coercivity. In addition, the temperature stability of coercivity was improved after the diffusion of Pr-Cu alloy.

Modelling of strain induced magnetic anisotropy in Au additive FePt thin films

L10 ordering at low temperature and controlled grain size are prerequisites for the fabrication of magnetic recording media. This can be achieved by several methods such as addition, under layer or over layer of third element in FePt. In the present work, the kinetics of L10 ordering in the presence of immiscible element Au is investigated by varying the Au concentration at different annealing temperatures. The structural analysis shows that the Au additive not only promotes the ordering at low temperature but also supports the textured growth along (001) plane. The magnetic measurements supported by theoretical simulations using Monte Carlo predicts that the enhancement in coercivity attributed to induced strain anisotropy and weakening of inter-granular exchange coupling may be due to presence of Au at grain boundaries.

Optimized composition and improved magnetic properties of Ce-Fe-B alloys

Good magnetic properties of Ce17Fe76.5B6Nb0.5Cu0.5Ga0.5 alloy were obtained in our previous study. In order to increase the Curie temperature of Ce-Fe-B alloy without reducing the magnetic performance, Co element was added to optimize the composition of Ce-Fe-B based alloy. The effect of Nb, Cu, Ga, Co co-addition on phase structures, magnetic characteristics, microstructure and Ce valence state weight of Ce-Fe-B alloy are discussed comprehensively. Magnetic properties of Jr = 0.43 T, Hci = 486 kA/m, (BH)max = 30 kJ/m3 and TC = 437.8 K were obtained in Ce17Fe74.5B6Nb0.5Cu0.5Ga0.5Co2.0 alloy. An obvious remanent magnetization enhancement, decreased recoil permeability and fully closed recoil loops are observed for the optimized alloys. The strengthened short range exchange coupling interaction between adjacent grains contributes to the increased remanence ratio. The synchrotron radiation X-ray absorption near-edge structure fitting result showed that the magnetic Ce3+ valence weight of optimized alloy increased, while the nonmagnetic Ce4+ valence weight decreased compared with the original alloy. Microstructure observations showed that the triple junctions of tetragonal main phase grains are rich in Cu, while Co element prefers to enter into CeFe2 phase. The improved magnetic properties are mainly due to the increased Ce3+ valence weight and strengthened intergranular exchange coupling interactions.

Effects of solvent and annealing on phase evolutions and magnetic properties of Nd2 (Fe, Co)14C hard magnetic powders prepared by mechanochemical method

Nanocrystalline Nd2 (Fe, Co)14C materials were synthesized by a mechanochemical method. Ball milling in organic solvent (hydrocarbon), Nd15Fe80.6Co4B0.4 alloy disproportionated into NdH2+δ, α-Fe (Co) and Fe7C3 phases. H2 was released from the NdH2+δ and Nd2 (Fe, Co)14C hard magnetic powders were obtained during the subsequent annealing under vacuum. The effects of hydrocarbon solvent species and annealing condition on phase evolutions and magnetic properties were studied systematically. It is found that the n-hexane is more easily decomposed and makes the disproportion reaction more completed than other common hydrocarbons, which favor the formation of permanent magnetic Nd2 (Fe, Co)14C phase. Scanning electron microscope and Henkel plot analysis verified microstructural and intergranular exchange coupling can be well controlled by the annealing process. The optimum magnetic properties with remanent magnetization 4πMr of 7.35 kG, maximum energy product (BH)max of 12.3 MGOe and coercivity iHc of 16.2 kOe were obtained in the sample ball milled in n-hexane and annealed at 800 °C for 2 min with a heating rate of 10 °Cs−1. The systemical study shows that this method is a promising way to synthesize nano-sized Nd2 (Fe, Co)14C hard magnetic powder suitable for the manufacture of bond permanent magnet.

Proposal of Granular-Type Cap Layer with High-$K_{u}$ CoPt Grains and Ferromagnetic Oxide Grain Boundaries for Full Granular Media

Investigation of magnetic properties and microstructure for the stacked media with Co80Pt20-30 vol% rare earth (RE) oxide (RE oxide: Gd2O3, Nd2O3, and Sm2O3) cap layers (CLs) deposited on a Co80Pt20-30 vol% B2O3 granular recording layer (GRL) was conducted. It was found that the employment of a granular-type CL with ferromagnetic oxide is effective to control intergranular exchange coupling of the magnetic grains in CoPt–B2O3 GRL while maintaining the granular structure of the CL. In this full granular media, continuous structure of columnar magnetic grains and grain boundaries from the GRL up to the CL can be observed. When a typical ferromagnetic oxide CL, such as CoPt–Gd2O3 (9 nm), is deposited on CoPt–B2O3 GRL (16 nm), the nucleation field is increased from 0.7 to 1.1 kOe, and the saturation field is reduced from 21.5 to 16 kOe which suggest that CoPt-RE oxide is promising for a CL.