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多重铁性材料研究VII---Bi2CrFeO6
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Double ordered perovskite-type Bi2CrFeO6 is theoretically described to be potential candidate for novel FiM-FE multiferroics from N. A. Spaldin from UCSB! Some attempts have been performed to grow it in the form of thin film and bulk ceramics! On this topic, I have email-discussions with Dr. F. M. Bai at USA.
check following!
----- Original Message -----
From: "Feiming Bai" <fmbemc@rit.edu>
To: "Yu Jian" <jyu@mail.tongji.edu.cn>
Sent: Friday, February 15, 2008 10:07 PM
Subject: RE: Bi2FeCrO6 paper
Hi Dr. Yu,
Thank you for instant reply.
I totally agree that the most important thing about Bi2FeCrO6 is to find the proper preparation window, film or bulk form.
Thank you for instant reply.
I totally agree that the most important thing about Bi2FeCrO6 is to find the proper preparation window, film or bulk form.
R: I very agree to develop proper preparation method to obtain ordered Bi2FeCrO6. Here, B-site ordering is for the first important thing!!! The present experiments showed disordered samples, in the form of both thin film and bulk ceramics. It is very bad for them to compare it with Spaldin's prediction!
But my gut feeling also tells me that the conductance of this materials also depends on its dimension and strain condition, which may change the band structure and stabilize some metastable phases.
R: sure, the strain and dimension not only affect the conductance but also the electrical and magnetic properties of Bi2FeCrO6. However, the published present experimental results could not definitely say many things on it. To my knowledge, the sample quality is still in problem for no one exactly know the strain condition windows to stablize perovskite structure and many impurity phases confuse it! Even in the samples synthesized by high-pressure methods, no one obtained very pure single phase sample till now!
In addition, you mentioned that the Tc of BFCO is higher than 400oC. In such a case, superexchange coupling seems not be able to fully explain it. If you got this result in bulk ceramics, strain engineering should be out of consideration too...
R: I never said "the Tc of BFCO is higher than 400oC"! my sample is not BFCO but BFCO-based solid solution! I said Tc_FM is above 400K. "1) the ferrimagnetic curie T is above RT for Bi2FeCrO6, not like by Spaldin;" mentioned in last email is just the result extrapolated from my experiments.
It is definitely an interesting result. I look forward to reading your paper.
Feiming Bai
-----Original Message-----
From: Yu Jian [mailto:jyu@mail.tongji.edu.cn]
Sent: Thu 2/14/2008 10:18 PM
To: Feiming Bai
Subject: Re: Bi2FeCrO6 paper
hi, Dr. Bai:
Thanks for your message.
First, happy chinese spring festival to you. I understand traveller's feeling around the world. ^_^
You are the first replier to my blog. welcome you discussion. On the review article, it is still in review even though I asked several times from the journal editor. When I get reviewer's comment and revise it, I will send you one copy.
On the paper about Bi2FeCrO6 solid solution, openmindedly, it is still in my desktop not published. Yes. I have performed this research about 41 monthes since I entered into multiferroics.
As you know, it is difficult for this field and much much difficult for any novel multiferroic system. Nevertheless, I would like share my opinion with you: the challenge of low resistivity is first difficulty for everyone in this field, in the case of BiFeO3, the present experimental results imply that it is extrinsic but you could not expect as high as in the case of ferroelectric titanates, the main difficulty comes from synthesization, which is bad not from performers but very from the characteristics of Bi2O3-Fe2O3 system. I have reviewed it in my review article.
Spaldin group's theoretical prediction is just theoretical prediction. Unfortunately, they have finished their calculation and prepared for publish just before three monthes ago I started thinking Cr-Fe d3-d5 as the origin of ferromagnetic order. Before I get definitely high qualified data, I do not want to publish it. ^-^ For it, 41 monthes have passed over. To my experiments, two things are encouraged: 1) the ferrimagnetic curie T is above RT for Bi2FeCrO6, not like by Spaldin; 2) at present, the previously published datas in the form of thin film and bulk are very condfused by poor sample, including unwanted phases which are high conductive! 3) one have to develop novel methods to synthesize metastable perovskite-type oxides including ordered Bi2FeCrO6 before judging the prediction by Spaldin group.
talk more next.
Best wishes
Jian Yu
----- Original Message -----
From: "Feiming Bai" <fmbemc@rit.edu>
To: "Yu Jian" <jyu@mail.tongji.edu.cn>
Sent: Friday, February 15, 2008 6:11 AM
Subject: Bi2FeCrO6 paper
Hi Dr. Yu,
How are you? I guess you had a really joyful and happy Spring Festival.
I read your blog at http://www.sciencenet.cn, and is interested in your coming review article about the challenges in single-phase ferromagnetic-ferroelectric multiferroic materials. I wonder if this paper is published. And can you send a copy to me (or other published paper about Bi2FeCrO6 solid solution)? Recently, there is some work about BFCO thin films, in which people have obtained Ms=30 emu/cc at room temperature. This is consistent with you previous research. But they were facing the challenge of low resistivity, and didn't give reliable saturated polarization value and Tc. I am curious if the high conduction is the intrinsic property of this material. This may kill the predicted Ps (=80 uc/cm2) by Spaldin group.
Thank you
Best regards,
Feiming Bai
https://blog.sciencenet.cn/blog-32670-16086.html
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